Crystal structure across the β to α phase transition in thermoelectric Cu2−xSe

Eikeland, E.; Blichfeld, A.B.; Borup, K.A.; Zhao, K.; Overgaard, J.; Shi, X.; Chen, L.; Iversen, B.B.

doi:10.1107/S2052252517005553

research papers

IUCrJ

Volume 4| Part 4| July 2017| Pages 476-485

ISSN: 2052-2525

https://doi.org/10.1107/S2052252517005553

CHEMISTRY | CRYSTENG

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Crystal structure across the β to α phase transition in thermoelectric Cu_2−xSe

Espen Eikeland,^a Anders B. Blichfeld,^a Kasper A. Borup,^a,^b Kunpeng Zhao,^c Jacob Overgaard,^a Xun Shi,^c Lidong Chen ^c and Bo B. Iversen ^a ^*

^aCenter for Materials Crystallography, Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Langelandsgade 140, Aarhus 8000-DK, Denmark, ^bNational Renewable Energy Laboratory, 15013 Denver W Pkwy, Golden, CO 80401, USA, and ^cState Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050, People's Republic of China
^*Correspondence e-mail: bo@chem.au.dk

Edited by C. Lecomte, Université de Lorraine, France (Received 30 November 2016; accepted 12 April 2017; online 13 June 2017)

The crystal structure uniquely imparts the specific properties of a material, and thus provides the starting point for any quantitative understanding of thermoelectric properties. Cu_2−xSe is an intensely studied high performing, non-toxic and cheap thermoelectric material, and here for the first time, the average structure of β-Cu_2−xSe is reported based on analysis of multi-temperature single-crystal X-ray diffraction data. It consists of Se–Cu layers with additional copper between every alternate layer. The structural changes during the peculiar zT enhancing phase transition mainly consist of changes in the inter-layer distance coupled with subtle Cu migration. Just prior to the transition the structure exhibits strong negative thermal expansion due to the reordering of Cu atoms, when approached from low temperatures. The phase transition is fully reversible and group–subgroup symmetry relations are derived that relate the low-temperature β-phase to the high-temperature α-phase. Weak superstructure reflections are observed and a possible Cu ordering is proposed. The structural rearrangement may have a significant impact on the band structure and the Cu rearrangement may also be linked to an entropy increase. Both factors potentially contribute to the extraordinary zT enhancement across the phase transition.

Keywords: thermoelectrics; negative thermal expansion; properties of solids; inorganic materials.

CCDC references: 1543669; 1543670; 1543671; 1543672; 1543673; 1543674; 1543675; 1543676; 1543677

1. Introduction

Thermoelectric (TE) materials can directly interconvert heat and electricity, and they potentially provide green sustainable solutions to global energy challenges (Bell, 2008 ; Heremans et al., 2013 ; Zhang & Zhao, 2015 ). However, large scale application requires the development of TE materials made from non-toxic and earth-abundant elements, and this continues to be a key challenge since high performing stable materials typically contain the rare element tellurium (e.g. in Bi₂Te₃ or PbTe). Cu_2−xSe, x ≃ 0, has been intensely studied as a promising cheap TE material (Miyatani, 1973 ; Vučić et al., 1982 , 1984 ; Liu et al., 2012 , 2013a ,b ; Yu et al., 2012 ; Brown et al., 2013a ; Chi et al., 2014 ; Mahan, 2015 ; Sirusi et al., 2015 ; Sun et al., 2015 ; Kang et al., 2016 ; Brown & Snyder, 2016 ), and recently a highly peculiar large increase in thermoelectric performance (zT) was observed just prior to the phase transition from the structurally unknown low-temperature β-Cu_2−xSe phase to the cubic high-temperature α-Cu_2−xSe phase (Brown et al., 2013a; Liu et al., 2013b; Brown & Snyder, 2016; Kang et al., 2016). The enhanced performance is too large to be successfully described using conventional band-theory calculations under the normal assumptions (Brown et al., 2013a; Mahan, 2015; Sun et al., 2015; Kang et al., 2016), and it has been suggested that the enhancement may be coupled to an entropy increase stemming from a structural rearrangement of the Cu ions (Brown & Snyder, 2016; Brown et al., 2016 ). A detailed understanding of this phenomenon requires knowledge of the crystal structure of the low-temperature β-phase. With regards to nomenclature, there has been some confusion in the literature how to label the low- and high-temperature phase of Cu_2−xSe. In this work we use the original nomenclature introduced by Rahlfs in 1936 (Rahlfs, 1936 ).

The maximum efficiency of a thermoelectric generator (Snyder & Toberer, 2008 ) is given by the thermoelectric figure of merit zT, $[zT = [({{{S}^{2}\cdot \sigma )}/{\kappa }}]T]$ , calculated from the Seebeck coefficient (S), the electrical conductivity (σ), the thermal conductivity (κ) and the absolute temperature (T). An important aspect of the Cu_2−xSe phase transition is that κ is normally determined from the thermal diffusivity, D_T, using $[\kappa = {c}_{P}\cdot \rho \cdot {D}_{T}]$ , where c_P is the specific heat capacity and ρ the density. If a phase transition takes place, c_P can be interpreted in different ways depending on the order of the transformation (Liu et al., 2013b; Brown et al., 2013a, 2016). For Cu_2−xSe the phase transition occurring around 400 K, with the exact value depending on x, has been reported both as a first- (Vučić et al., 1984; Kang et al., 2016) and a second-order transition (Liu et al., 2013a,b; Brown et al., 2013a; Sirusi et al., 2015; Mahan, 2015; Brown & Snyder, 2016). Without a clear understanding of the nature of the phase transition, the zT value of Cu_2−xSe cannot be established correctly.

The development of Cu_2−xSe as a high performing thermoelectric material represents an excellent example of empirical materials optimization in which a fundamental understanding of the system is lacking. In general, the crystal structure imparts the specific intrinsic TE properties of a given material, and thus rational improvement of existing materials, or the design of new materials, necessarily has to be based on knowledge of the atomic structure of the material. Indeed, great progress has been achieved by materials' genome-like theoretical calculations of transport properties based on known crystal structures. This, for example, led to the discovery of the colossal thermopower in FeSb₂ (Bentien et al., 2006 , 2007 ; Peijie et al., 2009 ; Søndergaard et al., 2013 ). However, most often new high-performance materials are discovered by highly time-consuming experimental screening, and for known materials the properties are empirically optimized, e.g. through systematic substitution or doping. In cases where the detailed crystal structure is unknown the origin of specific properties is unclear and efficient optimization strategies are difficult to develop. In this respect β-Zn₄Sb₃ is a good example. This material caused excitement when it was (re)discovered in the 90s (Caillat et al., 1997 ), but it was only 10 years later when the detailed crystal structure was solved that the origin of the extraordinary properties could be rationalized (Cargnoni et al., 2004 ; Snyder et al., 2004 ). Similarly, a very large literature exists on PbTe (Heremans et al., 2008 ; Pei et al., 2011 ; Biswas et al., 2012 ; Christensen et al., 2016 ), but only very recently the details of the cation defect and disordered crystal structure were established, potentially paving the way for obtaining a quantitative understanding of its outstanding properties (Božin et al., 2010 ; Christensen et al., 2016). The insufficient structural information regarding the β-Cu_2−xSe phase is not the result of lacking effort. Already in 1936 Rahlfs (1936) concluded that β-Cu_2−xSe does not adopt the simple antifluorite structure of the α-phase. In 1987 Milat et al. proposed a monoclinic super-cell by combining X-ray and electron diffraction (Milat et al., 1987 ). Furthermore, the publication contains an overview of 10 different unit cells proposed by previous researchers. A full structure based on single-crystal X-ray diffraction (SCXRD) data has been reported by Gulay et al. (2011 ), but their proposed structural model did not describe their own diffraction data well resulting in high residuals with R₁ ≃ 0.14. When the structural model of Gulay et al. is fitted to the present higher quality SCXRD data with fixed coordinates and atomic displacement parameters (ADPs), (scale factor refinement only), a very high R₁ value of 0.600 is obtained, whereas free refinement of scale, positions and ADPs results in R₁ = 0.294. This shows that the Gulay model is clearly incorrect. In recent years the β-phase has been studied using pair distribution function and density functional theory analysis (Brown et al., 2013b ; Brown & Snyder, 2016). Still, as acknowledged widely in the literature, no satisfying structural model has yet been proposed (Milat et al., 1987; Kashida & Akai, 1988 ; Yamamoto & Kashida, 1991 ; Frangis et al., 1991 ; Gulay et al., 2011; Nguyen et al., 2013 ; Lu et al., 2015 ; Brown & Snyder, 2016). Herein we report the average crystal structure of the low-temperature β-phase of Cu_2−xSe, based on analysis of SCXRD data. The structural changes as the critical temperature is approached are established, and connected to the high-temperature α-phase through symmetry relations. The average structure is further used to model high-resolution synchrotron powder X-ray diffraction (PXRD) data.

An overview of the transport properties for Cu_2−xSe, with temperature, is given in Fig. 1. Overall the properties can be split into five distinct temperature regions (1–5), as indicated. In general, the measured physical properties are in good agreement between studies, taking the difference in copper deficiencies into account (Yu et al., 2012; Liu et al., 2012, 2013a,b; Brown et al., 2013a; Ballikaya et al., 2013 ; Chi et al., 2014; Zhao et al., 2015a ,b ; Yang et al., 2015 ; Kang et al., 2016). In regions 1, 3 and 5 the TE properties change monotonically in an overall beneficial way, increasing zT (Yu et al., 2012; Liu et al., 2012; Zhao et al., 2015a,b). Region 5 corresponds to the known high-temperature α-phase, having attractive TE properties for 0 ≤ x < 0.25. The cubic α-phase has been studied as a promising TE material, although since the material is also a superionic conductor this poses an intrinsic challenge with regards to designing TE modules (Brown et al., 2013b). In region 2 (80–165 K) abrupt changes in the Hall mobility indicates another phase transition as proposed by Chi et al. (2014), although not observed in the present diffraction data.

Figure 1
Published thermoelectric data for Cu_2−xSe. (a) Seebeck coefficient (S), (b) resistivity (ρ) and (c) hall mobility ( $[{\mu _{\rm Hall}}]$ ) from selected publications to illustrate the trend in the TE properties for Cu₂Se. The references used are Liu et al. (2012

), Yu et al. (2012

), Ballikaya et al. (2013

), Zhao et al. (2015b

), Chi et al. (2014

), Liu et al. (2013b

) and Brown et al. (2013a

In the temperature range 350–410 K, region 4 in Fig. 1, where the phase transition takes place, most of the physical properties change substantially (Liu et al., 2013a,b; Brown et al., 2013a; Ballikaya et al., 2013; Chi et al., 2014; Kang et al., 2016). The exact temperatures for the onset and termination of the transformation are governed by the copper deficiency with higher copper content narrowing the temperature range from both ends (Takahashi et al., 1976 ; Vučić et al., 1984). Upon heating a change in the slope of σ is observed around 350 K (Liu et al., 2013a,b; Brown et al., 2013a; Ballikaya et al., 2013; Chi et al., 2014; Kang et al., 2016) coinciding with an observed change in the ion conductivity (Miyatani, 1973; Vučić et al., 1982; Sirusi et al., 2015). The increased copper ionic conductivity is linked to structural changes since dilatometry measurements by Vučić et al. showed that changes in the thermal expansion also coincide with the change in σ (Vučić et al., 1982, 1984; Horvatić & Vučić, 1984 ). Very interestingly, negative thermal expansion (NTE) has been observed just prior to the phase transition. Below T_c there is a sharp drop in κ, D_T, σ, electronic mobility ( $[{\mu _e}]$ ), and charge carrier concentration (n), whereas there is a peak in S (Vučić et al., 1982; Liu et al., 2013a,b; Brown et al., 2013a; Kang et al., 2016). In combination this leads to the enhancement of zT (Brown et al., 2013a; Liu et al., 2013b; Brown & Snyder, 2016; Kang et al., 2016). Brown et al. related the increase in zT to the contribution from S, and it was believed to stem from an increase in entropy when there is an increase in the mobility of Cu ions (Brown & Snyder, 2016). Liu et al. explains the peak in zT by the influence of structural fluctuations on the increase in scattering of charge carriers and phonons (Liu et al., 2013a). Mahan has given a theoretical explanation for the peak in S as being due to a broadening of the conduction band energy immediately before T_c (Mahan, 2015). The broadening can possibly originate from various different effects, but was suggested to `probably [be] due to critical fluctuations' along the same lines as Liu et al. (2013a,b). Yet another explanation was proposed by Sun et al., who showed that a large change in $[{\mu _e}]$ will give rise to an extra contribution to S (Sun et al., 2015). In all these studies a better structural model is clearly needed for β-Cu_2−xSe in order to understand the differences in properties across the phase transition (Brown et al., 2013a; Chi et al., 2014; Sirusi et al., 2015; Brown & Snyder, 2016; Kang et al., 2016). A final point to note is that Cu_2−xSe in the literature often is referred to as a `phonon–liquid electron-crystal (PLEC)' since the disordered nature of the Cu ions in the crystal structure is believed to strongly influence the phonon heat transport (Liu et al., 2012). If one disregards the region around the phase transition, then the thermal diffusivity is similar in value between the low-temperature and the high-temperature Cu_2−xSe phases (Kang et al., 2016). This suggests that a complete understanding of the phonon scattering processes in Cu_2−xSe may not have been reached.

2. Experimental

Single crystals of β-Cu_2−xSe were grown using chemical vapor transport (CVT) with iodine and bromine as transport agents. A Cu_2.2Se precursor was synthesized by direct reaction between elemental copper (99.99%, Alfa Aesar) and selenium (99.999+%, Alfa Aesar) in a sealed quartz ampoule (< 10⁻⁴ mbar). The ampoule was heated in a vertical tube furnace to 873 K at 100 K h⁻¹ and soaked for 10 h for pre-reaction. The furnace was then heated to 1273 K at 100 K h⁻¹ and soaked for 42 h for final reaction and homogenization. The resulting ingot was coarsely ground using an agate mortar in air and loaded into two new ampules for CVT crystal growth. The ampoules were cleaned in 20 M NaOH at 423 K for 30 min and thoroughly rinsed and soaked overnight in Milli-Q water to improve the quartz surface and reduce the number of nucleation sites. 3.9 g of the ground precursor was loaded in the two ampoules and 20 mg elemental iodine and 32 mg CuBr₂ was added as transport agents, respectively. The ampoules were sealed with a vacuum (< 10⁻⁴ mbar) and the precursor material was carefully moved to the end where the ampoule was sealed to allow crystal growth on the treated surface of the ampoule (no visible material was left). The ampoules had an inner diameter of 10 mm and a length of 20 cm and were placed side-by-side in a horizontal two-zone tube furnace (without being in contact) for crystal growth. The growth zone was heated to 1273 K and the source zone to 1223 K and soaked for 3 days. This ensured a clean surface for crystal growth. After the back-transport period the temperature gradient was reversed by first cooling the growth zone to 1223 K and then heating the source zone to 1273 K. After 2 weeks the source zone was cooled to 1225 K and then both the source and growth zones were simultaneously cooled to room temperature. Since only little growth was observed the ampoules were reloaded in the furnace and the process was repeated but with the source and growth zones at 1298 K and 1198 K, respectively. Limited transport was still observed, but significant ripening and crystal growth was obtained in the source zone and a single crystal (0.09 × 0.05 × 0.02 mm³) from the hot end of the CuBr₂ ampoule was selected for SCXRD.

A bulk sample with a total mass of 3.275 g was prepared by first melting a stoichiometric ratio of the elements Cu (shot, 99.999%, Alfa Aesar) and Se (shot, 99.999%, Alfa Aesar) in a pyrolytic boron nitride (P-BN) crucible enclosed in a fused silica tube at 1423 K for 12 h in vacuum, and then slowly cooled down to 923 K in 96 h, where the material was held for 6 days. Finally, the tube was slowly cooled down to room temperature in 50 h.

Multi-temperature SCXRD experiments were carried out on a SuperNova diffractometer from Agilent Technologies, using Mo Kα radiation (λ = 0.71073 Å), with the temperature regulated by a cryostat from Oxford Cryosystems. Diffracted intensities were collected on a CCD detector and the data integrated and corrected for absorption using CrysAlisPro (Xcalibur, 2010 ). The structure solution and refinement were carried out with SHELXT and SHELXL, respectively, using the Olex2 GUI (Dolomanov et al., 2009 ; Sheldrick, 2015 ).

PXRD were collected on the bulk polycrystalline sample at the SPring-8 synchrotron facility (BL44B2 beamline) using a wavelength of λ = 0.500266 (5) Å. Data were collected at 300, 200 and 100 K in that specific order not to induce any thermal hysteresis. The data were analyzed by Rietveld refinements performed in the MAUD program (Lutterotti, 2010 ). The instrumental contribution to the peak widths was determined from refinement of data collected on a NIST 674b CeO₂ powder standard, which was also used for wavelength determination. The main phase was modelled using the new average low-temperature structure from SCXRD (see details below), and a secondary cubic (high temperature) phase was included at all temperatures; α-Cu_2−xSe with x = 0.25 (ICSD-150758). The cell parameters and the phase fraction were refined for each phase. The β-Cu_2−xSe phase was modeled using an anisotropic particle size, also incorporating microstrain. This advanced model allows the refinement of different peak widths depending on the hkl values according to Popa (1998 ), which arise from the intrinsic platelet particle shape inherent to most layered structures. The particle shape was extended to L_max = 8, giving 10 refinable parameters for the particle size. For microstrain, there are 4 parameters available for refinement in the $[R\overline 3m]$ space group. Unit-cell parameters, and the x and y atomic coordinates were refined and constrained so that Cu2 stayed on the mirror plane. The atomic coordinates were refined for all general Wyckoff sites. The ADPs (U_iso) were refined for all atoms, with Cu1a and Cu1b constrained to have equivalent ADPs. Furthermore, the summed occupancy for Cu1a and Cu1b was constrained to be fully occupied. The results from the refinements of β-Cu_2−xSe, including the copper deficient α-Cu_2−xSe phase, are listed in Table S10 of the supporting information. The α-Cu_2−xSe phase was refined using an isotropic particle size model incorporating microstrain. The atomic x coordinate for Cu2 on the tetrahedral site was refined, plus all the ADPs and occupancies for Cu1 and Cu2.

3. Establishing the average crystal structure of the β-phase

In order to characterize the crystal structure of the β-phase a suitable single crystal with dimensions 0.09 × 0.05 × 0.02 mm³ was selected under a microscope, and SCXRD data were measured on a conventional laboratory (SuperNova) diffractometer. The average structure was solved by intrinsic phasing resulting in the space-group symmetry $[R\overline 3m]$ with cell parameters a = 4.1227 (8) Å, c = 20.449 (6) Å at 100 K, using the hexagonal unit-cell setting. The structure is deposited in the Cambridge Structural Database (1543669–1543677). Many of the proposed unit cells in the literature could be used to successfully index the reciprocal lattice, although only upon integration and comparing equivalent reflections the trigonal symmetry of the high-intensity reflections was established (see the supporting information for more details). The unit-cell parameters are almost identical to those proposed by Vučić et al. in 1981 with cell parameters a = b = 4.10 × 3 Å, c = 20.37 × 2 Å, α = γ = 90° and β = 120° found using electron diffraction (Vučić et al., 1981 ). Vučić et al. as well as previous researchers, also noted the occurrence of supercell reflections (indicated above by the multiplied integers) (Milat et al., 1987; Frangis et al., 1991). Superstructure reflections are also observed in the diffraction data obtained in the present work and therefore the structure found by only including the high-intensity reflections can be viewed as an average structure. The low-intensity superstructure reflections contain information about the difference between the superstructure and the proposed average structure. The implications of a superstructure are discussed below and more details concerning refinements of various superstructure models are given in the supporting information. Unfortunately, at this point no accurate description of the full superstructure is available, and the present paper therefore focuses on reporting the average crystal structure.

The average structure of β-Cu_2−xSe is displayed in Fig. 2, with selected crystallographic information listed in Table 1. The structure consists of hexagonal close packed (c.p.) Se layers stacked along the c-axis, with Cu atoms located slightly above and below the c.p. layers, with additional disordered copper located between every alternate layer. The asymmetric unit consists of a single Se position and two disordered copper sites (Cu1 and Cu2). Se and Cu1 are both located on threefold rotation axes with the Cu1 site splitting into two (Cu1a and Cu1b) positions located slightly above and below the Se layer. Cu2 is slightly shifted away from the threefold rotation axis. Freely refining occupancies of the two copper sites (Cu1 and Cu2) resulted in an overall stoichiometry of Cu_1.94 (2)Se at 100 K. However, the stoichiometry derived from SCXRD analysis is generally not well determined, in particular for disordered structures, since the occupancies correlate with ADPs. The elemental composition was therefore measured using energy dispersive X-ray spectrometry (EDX) on a single crystal from the same batch revealing a composition of Cu_1.95 (13)Se. In all the following structural refinements the Cu content was fixed to the value derived from EDX. The crystal structure has two different inter-layer distances, 3.067 (1) Å and 3.742 (1) Å at 295 K, with the longer distance being between layers containing the disordered copper, Fig. 2. The present structural motif is in good agreement with three previous structural models suggested from theoretical calculations, although they propose different unit-cell parameters (Fig. S14) (Liu et al., 2013b; Lu et al., 2015). As theoretical calculations in general do not accommodate disordered atomic positions, the three theoretical models differ in their arrangement of Cu atoms. Despite this the calculated energies for the three phases are almost identical, indicating that different ordering of the Cu atoms has similar energies. This corroborates that the Cu atoms are disordered on the length scale probed in our diffraction experiment. However, as discussed below a superstructure with ordered Cu atoms might possibly be found using a large supercell. The diffraction experiments carried out on the high-temperature α-phase showed the well known cubic structure with a = 5.8538 (3) Å at 400 K. The structure consists of cubic close-packed Se with disordered Cu located at the tetrahedral sites, splitting in two positions, the tetragonal site and one slightly shifted along the body-diagonal. In the structural model the ADPs of the two Cu sites are constrained to have the same value and the overall stoichiometry fixed to Cu_1.95Se.

Table 1
Crystallographic data for the β-Cu_2−xSe and α-Cu_2−xSe structure, including atomic coordinates

The structure solutions and refinements were carried out with SHELXT and SHELXL, respectively. The empirical multi-scan correction was used to account for absorption.

	β-Cu_2−xSe	α-Cu_2−xSe
Chemical formula†	Cu_1.95Se	Cu_1.95Se
Space group	$[R\bar 3m]$ ; H	$[Fm\bar 3m]$
Temperature (K)	295	400
a (Å)	4.1227 (8)	5.8538 (3)
c (Å)	20.449 (6)	–
V (Å³)	301.0 (2)	200.59 (3)
Z	6	4
ρ_calc (g cm⁻³)	6.711	6.707
μ (mm⁻¹)	38.277	38.257
F(000)	543	362
(sin θ/λ)_max (Å⁻¹)	0.62	0.62
T_min, T_max	0.17, 1.00	0.32, 1.00
N_Tot,obs	809	277
N_Uniq,obs	102	22
N_Parameters	19	6
GOF	1.210	1.261
R_int	0.075	0.079
R₁, R₁[F² > 2σ(F²)]	0.061, 0.059	0.043, 0.043
wR₂, wR₂[F² > 2σ(F²)]‡	0.158, 0.156	0.087, 0.087
Δρ_max, Δρ_min (e Å⁻³)	1.33, −1.39	0.50, −0.91

	Position (x, y, z)	Wyckoff position	Occupancy	U_eq (Å²)
β-Cu_2−xSe (295 K)
Se	[0, 0, 0.2416 (1)]	6c	1	0.025 (1)
Cu1a	[0, 0, 0.119 (1)]	6c	0.34 (3)	0.045 (5)
Cu1b	[0, 0, 0.0720 (8)]	6c	0.64 (3)	0.054 (5)
Cu2	[0.263 (1), 0.526 (2), 0.0255 (3)]	18h	0.322 (6)	0.051 (3)

α-Cu_2−xSe (400 K)
Se	(0, 0, 0)	4a	1	0.042 (2)
Cu1§	(1/4, 1/4, 1/4)	8c	0.61 (2)	0.071 (4)
Cu2	[0.339 (4), 0.339 (4), 0.339 (4)]	32f	0.091 (6)	0.071 (4)

†The copper content is restrained to the result from the elemental analysis.
‡ $[w = {{1}/\left[{{\sigma }^{2}\left({F}_{\rm o}^{2}\right)+{(aP)}^{2}+bP}\right]}]$ , P = (F_o² + 2F_c²)/3. a = 0.098 and b = 11.93 at 295 K. a = 0 and b = 16.35 at 400 K.
§In the α-Cu_2−xSe refinement the copper atoms are constrained to having the same ADPs.

Figure 2
The crystal structure of β-Cu_2−xSe. (a) The full unit cell is shown with the copper-rich layers highlighted by purple tetrahedra. (b) The structure oriented in the ab-plane is shown to the right. Color codes for the atoms are: Cu1a (blue), Cu1b (red), Cu2 (green) and Se (grey).

4. Structural changes across the phase transition in Cu_2−xSe

In order to characterize the structural changes leading up to the phase transition diffraction data were collected at multiple temperatures. Data were first collected at 100 K, 295 K and 400 K. At 400 K the phase transition is complete and data were then measured at 355 K, 380 K, 365 K and 372 K in that sequence determining T_c to lie somewhere between 372 K and 380 K for this specific sample. The phase transition was found to be completely reversible without noticeable degradation in the crystal quality. In the high-temperature α-phase Cu_2−xSe has the antifluorite structure with cubic close packed Se atoms and with disordered Cu atoms at all the tetrahedral sites, and along the body diagonal. It should be noted that it has been debated whether the Cu disorder is static or dynamic (Danilkin et al., 2012 ).

Normalized unit-cell parameters as a function of temperature are shown in Fig. 3(a) with the last two data points being from the high-temperature α-phase. The data clearly show that there is NTE just before the phase transition. This has also been observed using dilatometry (Vučić et al., 1984), and from 355 K to 372 K the unit-cell volume decreases 0.41 (3) %. After the phase transition the unit-cell volume starts to increase with temperature. The NTE is highly anisotropic being caused uniquely by a decrease in length of the c-axis, which is directly related to changes in the two inter-layer distances plotted in Fig. 3(b). The linear expansion along the c-axis, α_c, from 355 K to 372 K amount to −3.2 × 10⁻⁴ K⁻¹. In this short temperature range the negative expansion is comparable to the expansion found in colossal NTE materials, e.g. BiNiO₃ (Azuma et al., 2011 ). The a- and b-axes increase linearly in the measured temperature range. The distance between the layers containing the interstitial copper atoms (Cu2) drastically shortens near T_c. The shrinkage is almost compensated by an increased distance between the empty c.p. layers without interstitial copper. It is evident that up to the phase transition the two distinct inter-layer distances continuously approach the same value as observed in the cubic α-phase, Fig. 3(b). The changes in inter-layer distances are correlated with a significant Cu migration from the copper rich to the copper deficient layer, as illustrated in Fig. 3(c). From 295 K to 372 K an amount of electron density corresponding to ¼ Cu atom migrates from Cu1b to the Cu1a position, while the Cu occupancies at the disordered Cu2 site remain constant up to T_c (see Fig. S12). It should be noted that the Cu occupancies correlate with its ADPs, and care should to be taken when interpreting absolute values of occupancies. However, since the observed changes in occupancies are large compared with the uncertainties, and the total occupancy at the Cu1 site remain constant (when freely refined) up to T_c, the migration is credible.

Figure 3
Multi-temperature structural data for Cu_2−xSe. (a) Normalized cell parameters for Cu_1.95Se. At 100 K the hexagonal cell parameters are a = 4.092 (1) Å, c = 20.459 (9) Å and V = 296.7 (2) Å³. (b) Changes in inter-layer distances as a function of temperature, red is the long distance and black short. The two last data points in both figures are from the cubic α-phase. All uncertainties are smaller than the size of the symbols. (c) Three stages of the copper movement from the thick copper rich layer (red) to the thinner copper deficient layer (black). Copper atoms are represented as spheres, with trapeze symbols indicating Cu sites disordered about a threefold rotation axis, while triangles indicate disordered copper tetrahedra in the α-phase.

5. Symmetry relations between the α- and β-phase

Recently Brown et al. (2016) suggested that the phase transition in Cu_2−xSe for x ≃ 0 is of second order or continuous, while other studies have reported it as a first-order transition (Brown et al., 2013a; Vučić et al., 1984; Kang et al., 2016). According to Landau Theory, during a continuous phase transition the space group of one phase must be a subgroup of the space group of the other phase (Müller, 2013 ). If a group–subgroup symmetry relation exists, i.e. if it is possible to relate the symmetry of the high-temperature α-phase to the symmetry of the low-temperature β-phase, then we cannot exclude that the phase transition is of second order. Furthermore, and more importantly for this work, the derivation of such symmetry relations adds credibility to the structural model.

In the following, such symmetry relations are derived leading to exceptional good agreement between predicted and observed atomic positions. The α- and β-Cu_2−xSe structures are found to be related through two simple symmetry reduction steps as illustrated in Fig. 4 and the full Bärninghausen-tree is given in Fig. S13. The first step involves the loss of cubic symmetry. The α-Cu_2−xSe structure has the cubic space-group symmetry $[Fm\overline 3m]$ , with a = 5.8538 (3) Å at 400 K (see Table 1). The loss of cubic symmetry results in an intermediate trigonal structure with space group, $[R \overline{3}m]$ , as depicted in Fig. 4(b). In this structure the disordered Cu position is split into two distinct sites, with only ¼ of the positions retaining the threefold rotation symmetry. No indication of this proposed intermediate structure is found in the present diffraction data.

Figure 4
Symmetry-related phase transitions in Cu_2−xSe. (a) The cubic α-structure. Se_α (grey, 4a, $[m\overline 3m]$ ), Cu1_α (blue, 8c, $[\bar 43m]$ ), Cu2_α (red, 32f, 3m). (b) Intermediate structure with symmetry reduction leading to split Cu positions. Se (grey, 3a, $[\overline 3m]$ ), Cu1_α (blue, 6c, 3m), Cu2a_α (red, 6c, 3m), Cu2b_α (green, 18h, m). (c) The β-Cu_2−xSe structure after symmetry lowering from the intermediate phase. Se_β (grey, 6c, 3m), Cu1a_β (blue, 6c, 3m), Cu1b_β (red, 6c, 3m), Cu2_β (green, 18h, m). The transparent yellow atoms are the resulting vacant sites.

The second symmetry reduction leading to the low-temperature β-phase is a doubling of the c-axis. Here each of the three distinct copper positions from the intermediate structure are split into two crystallographically independent positions, while retaining their site symmetries. The atomic positions calculated by applying the symmetry reductions to positions of the cubic structure (at 400 K) can now be compared directly with the observed experimental positions for the β-structure, Fig. 4(c). Half of the Cu positions are vacant and this results in the observed layered structure with alternating Cu rich and Cu deficient layers. Furthermore, the Se position, which now has an unrestricted z coordinate, is shifted by 0.2 Å. This results in the two different inter-layer distances of 3.1 and 3.7 Å (at 295 K). Interestingly, the Cu1 position is shifted only 0.2 Å, while the disordered Cu2 site is shifted 0.7 Å when going through the phase transition closing in on the threefold rotation axis. This nicely illustrates that our single crystal of Cu_2−xSe undergoes an order–disorder transition in combination with a displacive phase transition. The widely assumed order–disorder nature of the transformation confirmed here should be seen in relation to the α-structure, i.e. the β-structure is more ordered than the α-structure, despite both structures containing disordered Cu positions.

6. Superstructure considerations

Although a full structure describing all superstructure peaks has not yet been found, it is informative to illustrate the discrepancies in the proposed models. A large monoclinic supercell with cell parameters, a = 7.154 (2) Å, b = 12.415 (3) Å, c = 27.440 (7) Å and β = 94.69 (2)° can index most of the observed superstructure reflections at 295 K. This cell indexes the same reflections as the unit cell proposed by Gulay et al. (2011). Integration using the large supercell also gives a reasonable R_int value of 0.085, when using the C2/c space-group symmetry. Owing to the similar unit cell proposed by Gulay et al. their proposed structural model was refined against our diffraction data. However, it quickly became clear that the Gulay structural model does neither fit the superstructure nor the high-intensity reflections resulting in very high residual values with R₁ = 0.570 and 0.610, respectively (scale factor refinement only). The R₁ values were calculated by dividing reflections into two groups; the high-intensity main reflections which are reflections also indexed by the average trigonal structure, and the superstructure reflections which are all the reflections indexed by the monoclinic supercell but not indexed by the average trigonal structure (see the supporting information §S3 and §S4 for more information). The integration using the monoclinic unit cell results in 236 main reflections and 2226 superstructure reflections at 295 K. Out of 2226 superstructure reflections 878 have I/σ > 2. The reason why the 295 K data are used instead of the 100 K data is that the diffraction data obtained at 100 K are slightly twinned.

In reciprocal space the b^*-axes of the monoclinic supercell and the average cell are overlapping and oriented in the same direction, but the b-axis of the monoclinic supercell is three times as long as for the average cell. This relation might qualitatively be explained by taking a closer look at the average structure, as a random distribution of Cu atoms on the two disordered Cu sites in the average structure leads to unrealistically short Cu—Cu distances. The short Cu—Cu distances are shown in Fig. 5 together with a possible local ordering of the Cu atoms in the ab-plane. Looking down the c-axis including only a single c.p. layer and the closest Cu sites, the shortest Cu1b—Cu2 distance of 2 Å cannot exist in the structure (shown as an orange bond in Fig. 5). If we remove the Cu1b site and keep the Cu1a atom located right on the other side of the c.p. layer, a realistic Cu1a—Cu2 distance of 2.7 Å is obtained. At 295 K the occupancies of Cu1b and Cu1a have a ratio of 2:1. This agrees with the copper ordering shown in Figs. 5(b) and (d), containing no short Cu—Cu distances. If the ordering is of long-range, this would result in a tripling of the a/b-axis. The described ordering of Cu sites has been incorporated into the monoclinic superstructure and refined against the diffraction data. However, the model did not fit the diffraction intensities with an overall R₁ of 0.378 for all reflections. From the constructed electron density difference map (Fig. S10) it is evident that in order to improve the model disordered Cu sites still need to be introduced into the structural model. By splitting 10 out of 12 Cu sites and incorporating anisotropic ADPs the fit improved considerably resulting in an overall R₁ of 0.119. This superstructure model accurately describes the main peak intensities (R₁ = 0.062), but the superstructure reflections have quite a poor residual (R₁ = 0.253). In order to progress and obtain a better structural model than the average structure reported here, better I/σ ratios for all superstructure reflections are needed. We have repeatedly tried to measure data using high brilliance synchrotron facilities, but in all cases poor crystal quality has led to worse data than reported here.

Figure 5
Proposed ordering of Cu atoms in a superstructure. The figure shows one c.p. layer where the copper atoms are disordered in the average structure [(a) and (c)] and the proposed superstructure [(b) and (d)]. (a) and (b) shows the ab-plane for disordered and ordered copper sites, respectively. In (c) and (d) the structure is seen from the top along the c-axis for disordered and ordered copper sites, respectively. Se (grey), Cu1a (blue), Cu1b (red) and Cu2 (green). The orange bond illustrates the unphysical short Cu1b—Cu2 contact.

Upon cooling the α-phase, weak supercell reflections emerge already at 372 K. When the sample is cooled to 100 K the intensity of the supercell reflections increases relative to the main reflections with a factor of ~5 (Table S9). This indicates that the superstructure is present up to the phase transition, but that thermal motion blurs the difference between the superstructure and the reduced cell of the average structure. The intensities of the supercell reflections at different temperatures are depicted in Fig. S8. Short-range order in the structure is also evident directly in the collected diffraction data as diffuse scattering. The diffuse scattering is most prominent along the reciprocal c*-axis.

7. Rietveld refinements of synchrotron PXRD data

To study the general applicability of the average structure of β-Cu_2−xSe, synchrotron PXRD data were measured on a polycrystalline bulk sample at three different temperatures, 100 K, 200 K and 300 K. The sample was found to also contain about 20 vol%, 25 vol% and 40 vol% of the cubic α-phase at 100, 200 and 300 K, respectively. The collected data are shown in Fig. 6 together with theoretical PXRD patterns for the structures published in the literature (Lu et al., 2015; Nguyen et al., 2013; Gulay et al., 2011). Superstructure peaks are indicated by black arrows. All the diffraction patterns show similar features with certain groups of reflections in the vicinity of the reflections from the experimental data, but none of the previously proposed structural models result in satisfactory Rietveld refinements (R_B < 0.02).

Figure 6
Synchrotron PXRD for the polycrystalline Cu_2−xSe sample. The insert is a zoom of the region where the supercell peaks are observed most clearly, marked by arrows. The theoretical diffraction patterns for the previously reported and related structures are shown in the lower panel for comparison. The α-Cu_1.75Se phase is ICSD-#150758.

In Fig. S14 the different structures are compared and even though the unit-cell parameters differ the structural similarities are obvious. The disorder on the copper sites together with higher symmetry is what sets the present average structure apart from the previously reported structures. By using the proposed average structure of β-Cu_2−xSe to model the PXRD data, refinements with low residuals were achieved. The resulting fits are plotted in Fig. S15 with the fitting parameters tabulated in Table S10. The average model fits the data extremely well, despite not including the weak superstructure features. The peak broadening is quite severe and needs to be well described in order to obtain good data fits. This is incorporated by using an anisotropic particle size model by Popa (1998). During the cooling process, some of the α-phase transforms into the β-phase, and at the same time the copper content in the remaining α-phase decreases, giving a composition of Cu_1.81Se, Cu_1.71Se and Cu_1.68Se for the cubic phase at 300, 200 and 100 K, respectively. The change in phase fraction and the copper content in the cubic phase indicates that copper is still quite mobile, even at low temperatures.

Upon cooling, the Cu in the β-phase moves from the copper-deficient layer Cu1a position to the C1b position in the copper-rich layer, as was also observed in SCXRD refinements (Table S10). The remaining parameters behave as expected. With the aid of the average structure new investigations of the phase diagram of Cu and Se are encouraged, since accurate phase fractions can now be extracted using Rietveld refinements.

8. Concluding remarks

Many structures related to Cu_2−xSe show similar physical properties such as A₂X, with A = Cu, Ag and X = S, Se, Te, but the zT enhancement near a phase transition is quite a new phenomenon. A similar but smaller zT enhancement was observed in the ion-conducting material AgCrSe₂ near T_c (Gascoin & Maignan, 2011 ). Interestingly, AgCrSe₂ has a similar structure to β-Cu_2−xSe, although in the former the phase transition does not result in a lattice distortion (Damay et al., 2016 ). In both the LT (R3m) and HT ( $[R\overline 3m]$ ) structure AgCrSe₂ forms a layered structure with Cr and Ag positioned in between adjacent c.p. Se layers at the octahedral and tetrahedral sites, respectively (Van Der Lee & Wiegers, 1989 ). In AgCrSe₂, the Seebeck enhancement is presumably related to a redistribution of the Ag ions during the phase transition. If the Seebeck enhancement in Cu_2−xSe up to the phase transition is related to the entropy carried by the Cu ions, then substituting Ag into the structure should increase the entropy carried by the ions and increase the effect. This is indeed observed for Cu_1.97Ag_0.03Se (Brown et al., 2013a).

Brown et al. (2016) showed that the peak in zT is due to the peak in S since $[\sigma \cdot T/\kappa]$ decreases and shows a minimum at the phase transition. The peak in S must therefore more than compensate for this minimum to result in the observed peak in zT. This has been interpreted by Brown et al. (Brown et al., 2013a; Brown & Snyder, 2016) as a coupling of the changing entropy of the Cu ions to the charge carriers across the phase transition, thus invoking the interpretation of the Seebeck coefficient as the entropy transported per charge carrier. The band structure was assumed to vary smoothly across the phase transition, hence disfavoring an explanation based on specific changes to the band structure.

In our study we observe a significant NTE and continuous changes in the inter-layer distances leading up to T_c. A decreasing unit-cell size can lead to an increased band gap, and a change in the inertial effective mass of the charge carriers (Zeier et al., 2016 ). In the single parabolic band model an increase in the effective mass will lead to a decrease in the electrical mobility and a peak in the resistivity (assuming constant carrier concentration) as observed in Fig. 1. In this picture the increase in the Seebeck coefficient may be explained by the increased effective mass. Mahan found that the increase in S can be explained by a broadening of the conduction band energy (Mahan, 2015). He suggested several possible explanations for such broadening including cation disordering, inhomogenous broadening or critical fluctuations. The present average structure may facilitate further work leading to an unambiguous explanation for the extraordinary properties of Cu_2−xSe.

In summary, we report the average structure of the low-temperature β-phase of Cu_2−xSe based on SCXRD, and the structure is shown to also provide an excellent fit to synchrotron PXRD using the Rietveld method. A potential ordering of the Cu atoms has been proposed based on the observation of weak superstructure reflections. As the temperature approaches the transition temperature the superstructure reflections disappear, indicating that at temperatures close to the transition temperature the average structure reported is a good approximation. The structural changes presented are likely important for the peculiar enhancement of zT during the β-to α-phase transition, which is governed by a redistribution of the Cu atoms. The widely assumed order–disorder character of the transition is confirmed, and specific group–subgroup symmetry relations were derived for the structures across the completely reversible phase transition.

Supporting information

CCDC references: 1543669; 1543670; 1543671; 1543672; 1543673; 1543674; 1543675; 1543676; 1543677

Crystal structure: contains datablocks global, Cu1p95Se_CVT1_100K, Cu1p95Se_CVT1_295K, Cu1p95Se_CVT1_355K, Cu1p95Se_CVT1_365K, Cu1p95Se_CVT1_372K, Cu1p95Se_CVT1_380K, Cu1p95Se_CVT1_400K, Cu2-xSe_CVT2_100K_afterheatingto450K, Cu2-xSe_bulk_100K. DOI: https://doi.org/10.1107/S2052252517005553/lc5071sup1.cif

Structure factors: contains datablock Cu1p95Se_CVT1_100K. DOI: https://doi.org/10.1107/S2052252517005553/lc5071Cu1p95Se_CVT1_100Ksup2.fcf

Structure factors: contains datablock Cu1p95Se_CVT1_295K. DOI: https://doi.org/10.1107/S2052252517005553/lc5071Cu1p95Se_CVT1_295Ksup3.fcf

Structure factors: contains datablock Cu1p95Se_CVT1_355K. DOI: https://doi.org/10.1107/S2052252517005553/lc5071Cu1p95Se_CVT1_355Ksup4.fcf

Structure factors: contains datablock Cu1p95Se_CVT1_365K. DOI: https://doi.org/10.1107/S2052252517005553/lc5071Cu1p95Se_CVT1_365Ksup5.fcf

Structure factors: contains datablock Cu1p95Se_CVT1_372K. DOI: https://doi.org/10.1107/S2052252517005553/lc5071Cu1p95Se_CVT1_372Ksup6.fcf

Structure factors: contains datablock Cu1p95Se_CVT1_380K. DOI: https://doi.org/10.1107/S2052252517005553/lc5071Cu1p95Se_CVT1_380Ksup7.fcf

Structure factors: contains datablock Cu1p95Se_CVT1_400K. DOI: https://doi.org/10.1107/S2052252517005553/lc5071Cu1p95Se_CVT1_400Ksup8.fcf

Structure factors: contains datablock Cu2-xSe_CVT2_100K_afterheatingto450K. DOI: https://doi.org/10.1107/S2052252517005553/lc5071Cu2-xSe_CVT2_100K_afterheatingto450Ksup9.fcf

Structure factors: contains datablock Cu2-xSe_bulk_100K. DOI: https://doi.org/10.1107/S2052252517005553/lc5071Cu2-x5e_bulk_100Ksup10.fcf

Supporting figures and tables. DOI: https://doi.org/10.1107/S2052252517005553/lc5071sup12.pdf

Computing details top

Data collection: CrysAlis PRO, Agilent Technologies, Version 1.171.37.35 (release 13-08-2014 CrysAlis171 .NET) (compiled Aug 13 2014,18:06:01) for Cu1p95Se_CVT1_100K; CrysAlis PRO 1.171.38.41 (Rigaku OD, 2015) for Cu1p95Se_CVT1_295K, Cu1p95Se_CVT1_355K, Cu1p95Se_CVT1_365K, Cu1p95Se_CVT1_372K, Cu1p95Se_CVT1_380K, Cu1p95Se_CVT1_400K, Cu2-xSe_CVT2_100K_afterheatingto450K, Cu2-xSe_bulk_100K. Cell refinement: CrysAlis PRO, Agilent Technologies, Version 1.171.37.35 (release 13-08-2014 CrysAlis171 .NET) (compiled Aug 13 2014,18:06:01) for Cu1p95Se_CVT1_100K; CrysAlis PRO 1.171.38.41 (Rigaku OD, 2015) for Cu1p95Se_CVT1_295K, Cu1p95Se_CVT1_355K, Cu1p95Se_CVT1_365K, Cu1p95Se_CVT1_372K, Cu1p95Se_CVT1_380K, Cu1p95Se_CVT1_400K, Cu2-xSe_CVT2_100K_afterheatingto450K, Cu2-xSe_bulk_100K. Data reduction: CrysAlis PRO, Agilent Technologies, Version 1.171.37.35 (release 13-08-2014 CrysAlis171 .NET) (compiled Aug 13 2014,18:06:01) for Cu1p95Se_CVT1_100K; CrysAlis PRO 1.171.38.41 (Rigaku OD, 2015) for Cu1p95Se_CVT1_295K, Cu1p95Se_CVT1_355K, Cu1p95Se_CVT1_365K, Cu1p95Se_CVT1_372K, Cu1p95Se_CVT1_380K, Cu1p95Se_CVT1_400K, Cu2-xSe_CVT2_100K_afterheatingto450K, Cu2-xSe_bulk_100K. Program(s) used to solve structure: ShelXT (Sheldrick, 2015) for Cu1p95Se_CVT1_295K, Cu1p95Se_CVT1_355K, Cu1p95Se_CVT1_365K, Cu1p95Se_CVT1_372K, Cu1p95Se_CVT1_400K, Cu2-xSe_CVT2_100K_afterheatingto450K, Cu2-xSe_bulk_100K; SHELXS (Sheldrick, 2008) for Cu1p95Se_CVT1_380K. For all compounds, program(s) used to refine structure: SHELXL (Sheldrick, 2015); molecular graphics: Olex2 (Dolomanov et al., 2009); software used to prepare material for publication: Olex2 (Dolomanov et al., 2009).

(Cu1p95Se_CVT1_100K) top

Crystal data top

0.33(Cu_5.85Se₃)	D_x = 6.812 Mg m⁻³
M_r = 202.86	Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3m	Cell parameters from 679 reflections
a = 4.0922 (10) Å	θ = 3.0–31.5°
c = 20.459 (9) Å	µ = 38.85 mm⁻¹
V = 296.7 (2) Å³	T = 100 K
Z = 6	Irregular, metallic grayish black
F(000) = 543	0.09 × 0.05 × 0.02 mm

Data collection top

SuperNova, Single source at offset, Atlas diffractometer	100 independent reflections
Radiation source: SuperNova (Mo) X-ray Source	100 reflections with I > 2σ(I)
Mirror monochromator	R_int = 0.107
Detector resolution: 10.3590 pixels mm^-1	θ_max = 26.3°, θ_min = 3.0°
ω scans	h = −5→5
Absorption correction: multi-scan CrysAlisPro, Agilent Technologies, Version 1.171.37.35 (release 13-08-2014 CrysAlis171 .NET) (compiled Aug 13 2014,18:06:01) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	k = −5→5
T_min = 0.098, T_max = 1.000	l = −24→23
754 measured reflections

Refinement top

Refinement on F²	19 parameters
Least-squares matrix: full	1 restraint
R[F² > 2σ(F²)] = 0.063	w = 1/[σ²(F_o²) + (0.0533P)² + 46.1849P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.152	(Δ/σ)_max < 0.001
S = 1.29	Δρ_max = 1.58 e Å⁻³
100 reflections	Δρ_min = −1.62 e Å⁻³

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Se1	0.3333	0.6667	0.42562 (14)	0.0173 (11)
Cu1B	0.6667	0.3333	0.4009 (6)	0.022 (3)	0.53 (3)
Cu2	0.4018 (11)	0.804 (2)	0.3077 (3)	0.035 (3)	0.332 (6)
Cu1A	0.6667	0.3333	0.4478 (13)	0.048 (8)	0.42 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Se1	0.0141 (12)	0.0141 (12)	0.0237 (18)	0.0070 (6)	0.000	0.000
Cu1B	0.018 (3)	0.018 (3)	0.028 (7)	0.0091 (16)	0.000	0.000
Cu2	0.046 (4)	0.029 (5)	0.024 (3)	0.014 (2)	0.0010 (12)	0.002 (2)
Cu1A	0.020 (5)	0.020 (5)	0.10 (2)	0.010 (2)	0.000	0.000

Geometric parameters (Å, º) top

Se1—Cu1Bⁱ	2.416 (3)	Cu2—Se1^xi	2.556 (4)
Se1—Cu1Bⁱⁱ	2.416 (3)	Cu2—Se1ⁱⁱⁱ	2.556 (4)
Se1—Cu1B	2.417 (3)	Cu2—Cu2^iv	2.150 (9)
Se1—Cu2ⁱⁱⁱ	2.556 (4)	Cu2—Cu2^v	0.840 (14)
Se1—Cu2^iv	2.556 (4)	Cu2—Cu2^vi	2.839 (6)
Se1—Cu2^v	2.460 (7)	Cu2—Cu2^xii	2.150 (9)
Se1—Cu2^vi	2.556 (4)	Cu2—Cu2^xiii	2.839 (6)
Se1—Cu2^vii	2.460 (7)	Cu2—Cu2^xi	2.308 (6)
Se1—Cu2	2.460 (7)	Cu2—Cu2^xiv	2.839 (6)
Se1—Cu1A	2.406 (5)	Cu2—Cu2ⁱⁱⁱ	2.308 (6)
Se1—Cu1Aⁱⁱ	2.406 (5)	Cu2—Cu2^vii	0.840 (14)
Se1—Cu1Aⁱ	2.406 (5)	Cu1A—Se1^viii	2.406 (5)
Cu1B—Se1^viii	2.416 (3)	Cu1A—Se1^xv	2.59 (3)
Cu1B—Se1^ix	2.416 (3)	Cu1A—Se1^ix	2.406 (5)
Cu1B—Cu1B^x	2.76 (2)

Cu1Bⁱ—Se1—Cu1Bⁱⁱ	115.75 (19)	Cu2ⁱⁱⁱ—Cu2—Se1^xi	158.0 (5)
Cu1Bⁱ—Se1—Cu1B	115.72 (19)	Cu2^xi—Cu2—Se1ⁱⁱⁱ	157.9 (5)
Cu1Bⁱⁱ—Se1—Cu1B	115.72 (19)	Cu2^iv—Cu2—Se1	67.0 (3)
Cu2^iv—Se1—Cu2ⁱⁱⁱ	18.9 (3)	Cu2^v—Cu2—Se1	80.18 (16)
Cu2^vii—Se1—Cu2ⁱⁱⁱ	50.7 (2)	Cu2^xii—Cu2—Se1	67.0 (3)
Cu2ⁱⁱⁱ—Se1—Cu2^vi	79.0 (3)	Cu2^vii—Cu2—Se1	80.17 (16)
Cu2^vii—Se1—Cu2^vi	50.7 (2)	Cu2^v—Cu2—Se1ⁱⁱⁱ	129.50 (17)
Cu2—Se1—Cu2^vii	19.7 (3)	Cu2^xi—Cu2—Cu2ⁱⁱⁱ	124.9 (5)
Cu2—Se1—Cu2ⁱⁱⁱ	54.76 (13)	Cu2^iv—Cu2—Cu2ⁱⁱⁱ	21.3 (4)
Cu2—Se1—Cu2^v	19.7 (3)	Cu2^vii—Cu2—Cu2^xiv	136.12 (13)
Cu2^v—Se1—Cu2ⁱⁱⁱ	68.91 (18)	Cu2^vii—Cu2—Cu2^v	60.001 (1)
Cu2^vii—Se1—Cu2^v	19.7 (3)	Cu2^v—Cu2—Cu2^xi	68.7 (4)
Cu2—Se1—Cu2^vi	68.91 (18)	Cu2^vii—Cu2—Cu2^iv	90.002 (6)
Cu2—Se1—Cu2^iv	50.7 (2)	Cu2^xi—Cu2—Cu2^xiv	14.6 (3)
Cu2^iv—Se1—Cu2^vi	94.16 (18)	Cu2^v—Cu2—Cu2^iv	139.15 (19)
Cu2^vii—Se1—Cu2^iv	54.76 (13)	Cu2^xi—Cu2—Cu2^vi	92.7 (3)
Cu2^v—Se1—Cu2^iv	68.91 (18)	Cu2^vii—Cu2—Cu2^xii	139.15 (19)
Cu2^v—Se1—Cu2^vi	54.75 (13)	Cu2^xii—Cu2—Cu2^xi	21.3 (4)
Cu1Aⁱ—Se1—Cu1Aⁱⁱ	116.5 (4)	Cu2^v—Cu2—Cu2^xii	90.002 (5)
Cu1Aⁱⁱ—Se1—Cu1A	116.5 (4)	Cu2^iv—Cu2—Cu2^xiv	109.5 (3)
Cu1Aⁱ—Se1—Cu1A	116.5 (4)	Cu2^vii—Cu2—Cu2^xiii	81.49 (13)
Se1^ix—Cu1B—Se1	115.73 (19)	Cu2^vii—Cu2—Cu2ⁱⁱⁱ	68.7 (4)
Se1^viii—Cu1B—Se1^ix	115.75 (19)	Cu2^v—Cu2—Cu2^xiii	136.12 (14)
Se1^viii—Cu1B—Se1	115.73 (19)	Cu2^vi—Cu2—Cu2^xiv	107.2 (2)
Se1^ix—Cu1B—Cu1B^x	102.1 (3)	Cu2^iv—Cu2—Cu2^xiii	11.16 (19)
Se1^viii—Cu1B—Cu1B^x	102.1 (3)	Cu2^xii—Cu2—Cu2ⁱⁱⁱ	114.2 (5)
Se1—Cu1B—Cu1B^x	102.1 (3)	Cu2^xii—Cu2—Cu2^xiii	109.5 (3)
Se1—Cu2—Se1ⁱⁱⁱ	125.25 (13)	Cu2^iv—Cu2—Cu2^xi	114.2 (5)
Se1—Cu2—Se1^xi	125.25 (13)	Cu2^xi—Cu2—Cu2^xiii	124.9 (5)
Se1ⁱⁱⁱ—Cu2—Se1^xi	106.4 (3)	Cu2^xiii—Cu2—Cu2^vi	92.2 (3)
Se1—Cu2—Cu2^vi	57.1 (2)	Cu2ⁱⁱⁱ—Cu2—Cu2^xiii	14.6 (3)
Se1—Cu2—Cu2^xiv	72.8 (2)	Cu2^v—Cu2—Cu2^xiv	81.49 (13)
Se1^xi—Cu2—Cu2^xiii	143.3 (3)	Cu2^iv—Cu2—Cu2^xii	98.3 (4)
Se1ⁱⁱⁱ—Cu2—Cu2^vi	109.2 (3)	Cu2^xii—Cu2—Cu2^xiv	11.16 (18)
Se1ⁱⁱⁱ—Cu2—Cu2^xiii	53.95 (12)	Cu2^vii—Cu2—Cu2^xi	121.5 (4)
Se1^xi—Cu2—Cu2^vi	124.42 (11)	Cu2ⁱⁱⁱ—Cu2—Cu2^xiv	124.9 (5)
Se1—Cu2—Cu2^xiii	72.8 (2)	Cu2^vii—Cu2—Cu2^vi	29.70 (19)
Se1ⁱⁱⁱ—Cu2—Cu2^xiv	143.3 (3)	Cu2^v—Cu2—Cu2ⁱⁱⁱ	121.5 (4)
Se1^xi—Cu2—Cu2^xiv	53.94 (12)	Cu2^v—Cu2—Cu2^vi	43.89 (14)
Cu2^vii—Cu2—Se1^xi	129.50 (17)	Cu2^xiii—Cu2—Cu2^xiv	120.6 (4)
Cu2^xi—Cu2—Se1	64.7 (3)	Cu2^iv—Cu2—Cu2^vi	96.3 (3)
Cu2^xii—Cu2—Se1ⁱⁱⁱ	138.3 (2)	Cu2^xii—Cu2—Cu2^vi	109.5 (3)
Cu2^v—Cu2—Se1^xi	80.54 (16)	Cu2ⁱⁱⁱ—Cu2—Cu2^vi	77.6 (5)
Cu2^vii—Cu2—Se1ⁱⁱⁱ	80.54 (16)	Se1^viii—Cu1A—Se1^ix	116.5 (4)
Cu2^iv—Cu2—Se1^xi	138.3 (2)	Se1^ix—Cu1A—Se1^xv	100.9 (6)
Cu2ⁱⁱⁱ—Cu2—Se1ⁱⁱⁱ	60.51 (18)	Se1^viii—Cu1A—Se1^xv	100.9 (6)
Cu2^xii—Cu2—Se1^xi	62.3 (2)	Se1^viii—Cu1A—Se1	116.5 (4)
Cu2ⁱⁱⁱ—Cu2—Se1	64.7 (3)	Se1—Cu1A—Se1^xv	100.9 (6)
Cu2^xi—Cu2—Se1^xi	60.50 (18)	Se1^ix—Cu1A—Se1	116.5 (4)
Cu2^iv—Cu2—Se1ⁱⁱⁱ	62.3 (2)

Symmetry codes: (i) x, y+1, z; (ii) x−1, y, z; (iii) −x+1/3, −y+5/3, −z+2/3; (iv) y−2/3, −x+y+2/3, −z+2/3; (v) −x+y, −x+1, z; (vi) x−y+1/3, x−1/3, −z+2/3; (vii) −y+1, x−y+1, z; (viii) x+1, y, z; (ix) x, y−1, z; (x) −x+4/3, −y+2/3, −z+2/3; (xi) −x+4/3, −y+5/3, −z+2/3; (xii) x−y+4/3, x+2/3, −z+2/3; (xiii) x−y+1/3, x+2/3, −z+2/3; (xiv) y+1/3, −x+y+2/3, −z+2/3; (xv) −x+1, −y+1, −z+1.

(Cu1p95Se_CVT1_295K) alpha-Cu2-xSe top

Crystal data top

0.33(Cu_5.85Se₃)	D_x = 6.711 Mg m⁻³
M_r = 202.76	Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3m	Cell parameters from 574 reflections
a = 4.1227 (8) Å	θ = 3.0–27.7°
c = 20.449 (6) Å	µ = 38.28 mm⁻¹
V = 301.00 (15) Å³	T = 295 K
Z = 6	Irregular, metallic grayish gray
F(000) = 543	0.09 × 0.05 × 0.02 mm

Data collection top

SuperNova, Single source at offset, Atlas diffractometer	99 reflections with I > 2σ(I)
Detector resolution: 10.3590 pixels mm^-1	R_int = 0.075
ω scans	θ_max = 26.3°, θ_min = 3.0°
Absorption correction: multi-scan CrysAlisPro 1.171.38.41 (Rigaku Oxford Diffraction, 2015) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	h = −5→5
T_min = 0.169, T_max = 1.000	k = −5→3
809 measured reflections	l = −24→24
102 independent reflections

Refinement top

Refinement on F²	19 parameters
Least-squares matrix: full	1 restraint
R[F² > 2σ(F²)] = 0.059	w = 1/[σ²(F_o²) + (0.0987P)² + 11.9258P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.158	(Δ/σ)_max < 0.001
S = 1.22	Δρ_max = 1.32 e Å⁻³
102 reflections	Δρ_min = −1.39 e Å⁻³

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Se1	0.3333	0.6667	0.42506 (12)	0.0245 (11)
Cu1B	0.6667	0.3333	0.4053 (8)	0.054 (5)	0.64 (3)
Cu2	0.140 (2)	0.0702 (11)	0.3589 (3)	0.051 (3)	0.322 (6)
Cu1A	0.6667	0.3333	0.4522 (10)	0.045 (5)	0.34 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Se1	0.0223 (12)	0.0223 (12)	0.0287 (17)	0.0112 (6)	0.000	0.000
Cu1B	0.029 (3)	0.029 (3)	0.104 (13)	0.0145 (14)	0.000	0.000
Cu2	0.049 (5)	0.058 (4)	0.043 (4)	0.025 (2)	−0.007 (3)	−0.0037 (13)
Cu1A	0.045 (5)	0.045 (5)	0.044 (12)	0.023 (3)	0.000	0.000

Geometric parameters (Å, º) top

Se1—Cu1Bⁱ	2.414 (3)	Cu2—Se1^ix	2.560 (4)
Se1—Cu1Bⁱⁱ	2.414 (3)	Cu2—Se1^vi	2.450 (6)
Se1—Cu1B	2.415 (3)	Cu2—Cu2^iv	2.150 (10)
Se1—Cu2ⁱ	2.560 (4)	Cu2—Cu2^xi	0.868 (14)
Se1—Cu2ⁱⁱⁱ	2.560 (4)	Cu2—Cu2^v	2.864 (7)
Se1—Cu2^iv	2.450 (6)	Cu2—Cu2^xii	2.150 (10)
Se1—Cu2^v	2.450 (6)	Cu2—Cu2^xiii	2.864 (7)
Se1—Cu2^vi	2.450 (6)	Cu2—Cu2^vi	2.319 (6)
Se1—Cu1Aⁱⁱ	2.444 (5)	Cu2—Cu2^xiv	2.864 (7)
Se1—Cu1Aⁱ	2.444 (5)	Cu2—Cu2^xv	2.319 (6)
Se1—Cu1A^vii	2.51 (2)	Cu2—Cu2^xvi	0.868 (14)
Se1—Cu1A	2.445 (5)	Cu1A—Se1^viii	2.444 (5)
Cu1B—Se1^viii	2.414 (3)	Cu1A—Se1^vii	2.51 (2)
Cu1B—Se1^ix	2.414 (3)	Cu1A—Se1^ix	2.444 (5)
Cu1B—Cu1B^x	2.94 (3)

Cu1Bⁱ—Se1—Cu1Bⁱⁱ	117.3 (2)	Cu2^vi—Cu2—Se1^ix	158.8 (6)
Cu1Bⁱ—Se1—Cu1B	117.2 (2)	Cu2^iv—Cu2—Se1^vi	67.3 (3)
Cu1Bⁱⁱ—Se1—Cu1B	117.2 (2)	Cu2^xvi—Cu2—Se1^vi	79.80 (16)
Cu2^vi—Se1—Cu2ⁱⁱⁱ	50.8 (2)	Cu2^xii—Cu2—Se1^vi	67.3 (3)
Cu2^iv—Se1—Cu2ⁱ	69.68 (18)	Cu2^xi—Cu2—Se1^vi	79.80 (16)
Cu2^iv—Se1—Cu2ⁱⁱⁱ	69.68 (18)	Cu2^iv—Cu2—Se1^ix	138.5 (2)
Cu2^v—Se1—Cu2ⁱⁱⁱ	55.08 (14)	Cu2^vi—Cu2—Cu2^xv	125.5 (6)
Cu2^vi—Se1—Cu2^v	20.4 (3)	Cu2^iv—Cu2—Cu2^xv	114.7 (5)
Cu2^vi—Se1—Cu2ⁱ	55.08 (14)	Cu2^xvi—Cu2—Cu2^xiv	29.4 (2)
Cu2^vi—Se1—Cu2^iv	20.4 (3)	Cu2^xvi—Cu2—Cu2^xi	60.001 (3)
Cu2ⁱⁱⁱ—Se1—Cu2ⁱ	19.5 (3)	Cu2^xii—Cu2—Cu2^xv	22.0 (4)
Cu2^v—Se1—Cu2^iv	20.4 (3)	Cu2^xvi—Cu2—Cu2^iv	89.999 (4)
Cu2^v—Se1—Cu2ⁱ	50.8 (2)	Cu2^vi—Cu2—Cu2^xiv	77.0 (5)
Cu1Aⁱ—Se1—Cu1A	115.0 (4)	Cu2^xi—Cu2—Cu2^iv	139.2 (2)
Cu1A—Se1—Cu1A^vii	76.9 (5)	Cu2^xii—Cu2—Cu2^v	109.8 (4)
Cu1Aⁱ—Se1—Cu1Aⁱⁱ	115.0 (4)	Cu2^xvi—Cu2—Cu2^xii	139.2 (2)
Cu1Aⁱⁱ—Se1—Cu1A	115.0 (4)	Cu2^xii—Cu2—Cu2^vi	114.7 (5)
Cu1Aⁱ—Se1—Cu1A^vii	76.9 (5)	Cu2^xi—Cu2—Cu2^xii	90.000 (4)
Cu1Aⁱⁱ—Se1—Cu1A^vii	76.9 (5)	Cu2^iv—Cu2—Cu2^xiv	96.3 (3)
Se1^ix—Cu1B—Se1	117.2 (2)	Cu2^xvi—Cu2—Cu2^xiii	43.96 (14)
Se1^viii—Cu1B—Se1	117.2 (2)	Cu2^xvi—Cu2—Cu2^xv	121.0 (4)
Se1^viii—Cu1B—Se1^ix	117.3 (2)	Cu2^xi—Cu2—Cu2^xiii	29.4 (2)
Se1—Cu1B—Cu1B^x	99.6 (4)	Cu2^v—Cu2—Cu2^xiv	92.1 (3)
Se1^viii—Cu1B—Cu1B^x	99.7 (4)	Cu2^iv—Cu2—Cu2^xiii	109.8 (4)
Se1^ix—Cu1B—Cu1B^x	99.7 (4)	Cu2^vi—Cu2—Cu2^v	15.1 (3)
Se1^vi—Cu2—Se1^ix	124.92 (14)	Cu2^xii—Cu2—Cu2^xiii	96.3 (3)
Se1^vi—Cu2—Se1	124.92 (14)	Cu2^iv—Cu2—Cu2^vi	22.0 (4)
Se1^ix—Cu2—Se1	107.2 (3)	Cu2^vi—Cu2—Cu2^xiii	92.6 (3)
Se1^vi—Cu2—Cu2^v	73.1 (3)	Cu2^xiii—Cu2—Cu2^v	107.5 (3)
Se1—Cu2—Cu2^v	53.34 (12)	Cu2^xv—Cu2—Cu2^xiii	77.0 (5)
Se1—Cu2—Cu2^xiii	124.20 (11)	Cu2^xi—Cu2—Cu2^xiv	43.96 (14)
Se1^ix—Cu2—Cu2^v	143.7 (3)	Cu2^iv—Cu2—Cu2^xii	98.4 (4)
Se1^ix—Cu2—Cu2^xiii	108.5 (3)	Cu2^xii—Cu2—Cu2^xiv	109.8 (4)
Se1^vi—Cu2—Cu2^xiii	57.0 (2)	Cu2^xvi—Cu2—Cu2^vi	68.0 (4)
Se1^vi—Cu2—Cu2^xiv	57.0 (2)	Cu2^xv—Cu2—Cu2^xiv	92.6 (3)
Se1^ix—Cu2—Cu2^xiv	124.20 (11)	Cu2^xi—Cu2—Cu2^vi	121.0 (4)
Se1—Cu2—Cu2^xiv	108.5 (3)	Cu2^xi—Cu2—Cu2^xv	68.0 (4)
Cu2^xvi—Cu2—Se1	80.24 (17)	Cu2^xvi—Cu2—Cu2^v	81.29 (13)
Cu2^vi—Cu2—Se1^vi	64.9 (3)	Cu2^xiii—Cu2—Cu2^xiv	17.4 (3)
Cu2^xii—Cu2—Se1^ix	62.0 (2)	Cu2^xi—Cu2—Cu2^v	136.04 (14)
Cu2^xi—Cu2—Se1	129.47 (18)	Cu2^iv—Cu2—Cu2^v	11.42 (18)
Cu2^xvi—Cu2—Se1^ix	129.47 (18)	Cu2^xv—Cu2—Cu2^v	125.7 (5)
Cu2^iv—Cu2—Se1	62.0 (2)	Se1^viii—Cu1A—Se1^ix	115.0 (4)
Cu2^xv—Cu2—Se1^ix	60.04 (18)	Se1^ix—Cu1A—Se1^vii	103.1 (5)
Cu2^xii—Cu2—Se1	138.5 (2)	Se1^viii—Cu1A—Se1^vii	103.1 (5)
Cu2^xv—Cu2—Se1^vi	64.9 (3)	Se1^viii—Cu1A—Se1	115.0 (4)
Cu2^vi—Cu2—Se1	60.03 (18)	Se1—Cu1A—Se1^vii	103.1 (5)
Cu2^xi—Cu2—Se1^ix	80.24 (17)	Se1^ix—Cu1A—Se1	115.0 (4)
Cu2^xv—Cu2—Se1	158.8 (5)

Symmetry codes: (i) x, y+1, z; (ii) x−1, y, z; (iii) −x+y, −x+1, z; (iv) y+1/3, −x+y+2/3, −z+2/3; (v) x−y+1/3, x+2/3, −z+2/3; (vi) −x+1/3, −y+2/3, −z+2/3; (vii) −x+1, −y+1, −z+1; (viii) x+1, y, z; (ix) x, y−1, z; (x) −x+4/3, −y+2/3, −z+2/3; (xi) −x+y, −x, z; (xii) x−y+1/3, x−1/3, −z+2/3; (xiii) y−2/3, −x+y−1/3, −z+2/3; (xiv) x−y−2/3, x−1/3, −z+2/3; (xv) −x+1/3, −y−1/3, −z+2/3; (xvi) −y, x−y, z.

(Cu1p95Se_CVT1_355K) top

Crystal data top

0.33(Cu_5.84Se₃)	D_x = 6.699 Mg m⁻³
M_r = 202.55	Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3m	Cell parameters from 336 reflections
a = 4.1299 (8) Å	θ = 3.0–27.8°
c = 20.393 (6) Å	µ = 38.21 mm⁻¹
V = 301.22 (15) Å³	T = 355 K
Z = 6	Irregular
F(000) = 542	0.09 × 0.05 × 0.02 mm

Data collection top

SuperNova, Single source at offset, Atlas diffractometer	98 reflections with I > 2σ(I)
Detector resolution: 10.3590 pixels mm^-1	R_int = 0.063
ω scans	θ_max = 26.2°, θ_min = 3.0°
Absorption correction: multi-scan CrysAlisPro 1.171.38.41 (Rigaku Oxford Diffraction, 2015) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	h = −4→5
T_min = 0.265, T_max = 1.000	k = −5→5
859 measured reflections	l = −24→24
102 independent reflections

Refinement top

Refinement on F²	19 parameters
Least-squares matrix: full	1 restraint
R[F² > 2σ(F²)] = 0.087	w = 1/[σ²(F_o²) + (0.156P)² + 17.1082P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.245	(Δ/σ)_max < 0.001
S = 1.25	Δρ_max = 1.97 e Å⁻³
102 reflections	Δρ_min = −3.19 e Å⁻³

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Se	0.3333	0.6667	0.42221 (17)	0.0388 (17)
Cu1B	0.6667	0.3333	0.4064 (17)	0.072 (9)	0.43 (4)
Cu2	0.3937 (17)	0.787 (3)	0.3029 (6)	0.089 (6)	0.329 (6)
Cu1A	0.6667	0.3333	0.4554 (11)	0.071 (5)	0.52 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Se	0.0340 (19)	0.0340 (19)	0.048 (3)	0.0170 (10)	0.000	0.000
Cu1B	0.040 (5)	0.040 (5)	0.14 (2)	0.020 (3)	0.000	0.000
Cu2	0.078 (7)	0.098 (14)	0.097 (7)	0.049 (7)	0.019 (3)	0.038 (7)
Cu1A	0.069 (6)	0.069 (6)	0.075 (12)	0.034 (3)	0.000	0.000

Geometric parameters (Å, º) top

Se—Cu1Bⁱ	2.406 (5)	Cu2—Se^xi	2.503 (7)
Se—Cu1Bⁱⁱ	2.406 (5)	Cu2—Cu2^v	2.314 (17)
Se—Cu1B	2.406 (5)	Cu2—Cu2^xii	2.906 (11)
Se—Cu2ⁱⁱⁱ	2.471 (11)	Cu2—Cu2^xiii	2.906 (11)
Se—Cu2^iv	2.471 (11)	Cu2—Cu2ⁱⁱⁱ	0.75 (2)
Se—Cu2^v	2.503 (7)	Cu2—Cu2^vi	2.432 (13)
Se—Cu2^vi	2.503 (7)	Cu2—Cu2^iv	0.75 (2)
Se—Cu2	2.471 (11)	Cu2—Cu2^xiv	2.906 (11)
Se—Cu1A^vii	2.50 (2)	Cu2—Cu2^xv	2.314 (17)
Se—Cu1Aⁱⁱ	2.479 (7)	Cu2—Cu2^xi	2.432 (13)
Se—Cu1Aⁱ	2.479 (7)	Cu1A—Se^ix	2.479 (6)
Se—Cu1A	2.479 (6)	Cu1A—Se^viii	2.479 (6)
Cu1B—Se^viii	2.406 (5)	Cu1A—Se^vii	2.50 (2)
Cu1B—Se^ix	2.406 (5)	Cu1A—Cu1A^xvi	3.00 (3)
Cu1B—Cu1B^x	2.98 (7)	Cu1A—Cu1A^xvii	3.00 (3)
Cu2—Se^vi	2.502 (7)	Cu1A—Cu1A^vii	3.00 (3)

Cu1Bⁱ—Se—Cu1Bⁱⁱ	118.2 (4)	Cu2^v—Cu2—Cu2^xiv	104.0 (6)
Cu1Bⁱ—Se—Cu1B	118.2 (4)	Cu2^v—Cu2—Cu2^vi	17.9 (6)
Cu1Bⁱⁱ—Se—Cu1B	118.2 (4)	Cu2ⁱⁱⁱ—Cu2—Cu2^xiii	32.9 (4)
Cu2ⁱⁱⁱ—Se—Cu2^vi	55.4 (4)	Cu2^xi—Cu2—Cu2^xii	116.7 (9)
Cu2^iv—Se—Cu2	17.4 (5)	Cu2^iv—Cu2—Cu2^xv	89.998 (9)
Cu2ⁱⁱⁱ—Se—Cu2	17.4 (5)	Cu2ⁱⁱⁱ—Cu2—Cu2^xiv	44.7 (2)
Cu2ⁱⁱⁱ—Se—Cu2^iv	17.4 (5)	Cu2ⁱⁱⁱ—Cu2—Cu2^xi	122.8 (6)
Cu2—Se—Cu2^v	55.4 (4)	Cu2^vi—Cu2—Cu2^xii	12.5 (4)
Cu2^iv—Se—Cu2^v	71.5 (3)	Cu2^xiv—Cu2—Cu2^xiii	14.8 (4)
Cu2ⁱⁱⁱ—Se—Cu2^v	58.5 (3)	Cu2^iv—Cu2—Cu2^vi	122.8 (6)
Cu2^vi—Se—Cu2^v	17.2 (5)	Cu2^vi—Cu2—Cu2^xiii	78.1 (7)
Cu2^iv—Se—Cu2^vi	71.5 (3)	Cu2^xv—Cu2—Cu2^vi	106.8 (8)
Cu2—Se—Cu2^vi	58.5 (3)	Cu2^v—Cu2—Cu2^xv	93.9 (7)
Cu1Aⁱⁱ—Se—Cu1A	112.8 (5)	Cu2^iv—Cu2—Cu2^xiv	32.9 (4)
Cu1A—Se—Cu1A^vii	74.1 (5)	Cu2^vi—Cu2—Cu2^xiv	90.7 (5)
Cu1Aⁱ—Se—Cu1A	112.8 (5)	Cu2ⁱⁱⁱ—Cu2—Cu2^xv	137.0 (3)
Cu1Aⁱⁱ—Se—Cu1Aⁱ	112.8 (5)	Cu2ⁱⁱⁱ—Cu2—Cu2^vi	72.1 (6)
Cu1Aⁱ—Se—Cu1A^vii	74.1 (5)	Cu2^iv—Cu2—Cu2^xi	72.1 (6)
Cu1Aⁱⁱ—Se—Cu1A^vii	74.1 (5)	Cu2^v—Cu2—Cu2^xi	106.8 (8)
Se^viii—Cu1B—Se^ix	118.2 (4)	Cu2^xii—Cu2—Cu2^xiv	103.1 (5)
Se^viii—Cu1B—Se	118.2 (4)	Cu2ⁱⁱⁱ—Cu2—Cu2^xii	82.6 (2)
Se^ix—Cu1B—Se	118.2 (4)	Cu2^iv—Cu2—Cu2^xiii	44.7 (2)
Se—Cu1B—Cu1B^x	97.7 (8)	Cu2^v—Cu2—Cu2^xiii	93.1 (5)
Se^viii—Cu1B—Cu1B^x	97.7 (8)	Cu2^xv—Cu2—Cu2^xiii	104.0 (6)
Se^ix—Cu1B—Cu1B^x	97.7 (8)	Cu2^iv—Cu2—Cu2^xii	135.3 (2)
Se—Cu2—Se^vi	121.5 (3)	Cu2^xi—Cu2—Cu2^xiii	90.7 (5)
Se—Cu2—Se^xi	121.5 (3)	Cu2^xv—Cu2—Cu2^xi	17.9 (6)
Se^vi—Cu2—Se^xi	111.2 (4)	Cu2^vi—Cu2—Cu2^xi	116.2 (10)
Se^xi—Cu2—Cu2^xii	142.6 (4)	Cu2^v—Cu2—Cu2^xii	10.1 (3)
Se^xi—Cu2—Cu2^xiv	111.7 (5)	Cu2^xii—Cu2—Cu2^xiii	90.6 (4)
Se^xi—Cu2—Cu2^xiii	125.56 (13)	Cu2ⁱⁱⁱ—Cu2—Cu2^v	89.998 (10)
Se—Cu2—Cu2^xiv	54.8 (4)	Cu2^xv—Cu2—Cu2^xiv	93.1 (5)
Se^vi—Cu2—Cu2^xiv	125.56 (12)	Cu2^xv—Cu2—Cu2^xii	104.0 (6)
Se^vi—Cu2—Cu2^xii	53.75 (19)	Cu2^xi—Cu2—Cu2^xiv	78.1 (7)
Se—Cu2—Cu2^xii	68.8 (5)	Cu2^iv—Cu2—Cu2^v	137.0 (3)
Se—Cu2—Cu2^xiii	54.8 (4)	Se^ix—Cu1A—Se^viii	112.8 (4)
Se^vi—Cu2—Cu2^xiii	111.7 (5)	Se^viii—Cu1A—Se	112.8 (4)
Cu2^v—Cu2—Se^vi	61.6 (3)	Se^ix—Cu1A—Se	112.8 (5)
Cu2^xv—Cu2—Se^xi	61.6 (3)	Se^viii—Cu1A—Se^vii	105.9 (5)
Cu2^xi—Cu2—Se^vi	154.5 (9)	Se^ix—Cu1A—Se^vii	105.9 (5)
Cu2^vi—Cu2—Se^vi	60.1 (3)	Se—Cu1A—Se^vii	105.9 (5)
Cu2^v—Cu2—Se	63.0 (5)	Se^ix—Cu1A—Cu1A^xvi	123.2 (4)
Cu2^vi—Cu2—Se	61.4 (5)	Se^vii—Cu1A—Cu1A^vii	52.7 (7)
Cu2ⁱⁱⁱ—Cu2—Se^vi	81.4 (3)	Se^viii—Cu1A—Cu1A^vii	123.2 (4)
Cu2^iv—Cu2—Se^xi	81.4 (3)	Se^viii—Cu1A—Cu1A^xvi	53.18 (18)
Cu2^iv—Cu2—Se^vi	132.5 (3)	Se^ix—Cu1A—Cu1A^vii	123.2 (4)
Cu2^vi—Cu2—Se^xi	154.5 (9)	Se^ix—Cu1A—Cu1A^xvii	53.18 (18)
Cu2ⁱⁱⁱ—Cu2—Se	81.3 (3)	Se—Cu1A—Cu1A^vii	53.18 (18)
Cu2^xv—Cu2—Se	63.0 (5)	Se^vii—Cu1A—Cu1A^xvii	52.7 (7)
Cu2^xi—Cu2—Se	61.4 (5)	Se—Cu1A—Cu1A^xvi	123.2 (4)
Cu2ⁱⁱⁱ—Cu2—Se^xi	132.5 (3)	Se^viii—Cu1A—Cu1A^xvii	123.2 (4)
Cu2^xv—Cu2—Se^vi	136.9 (3)	Se^vii—Cu1A—Cu1A^xvi	52.7 (7)
Cu2^xi—Cu2—Se^xi	60.1 (3)	Se—Cu1A—Cu1A^xvii	123.2 (4)
Cu2^iv—Cu2—Se	81.3 (3)	Cu1A^xvi—Cu1A—Cu1A^xvii	87.0 (10)
Cu2^v—Cu2—Se^xi	136.9 (3)	Cu1A^xvi—Cu1A—Cu1A^vii	87.0 (10)
Cu2ⁱⁱⁱ—Cu2—Cu2^iv	60.001 (5)	Cu1A^xvii—Cu1A—Cu1A^vii	87.0 (10)

Symmetry codes: (i) x−1, y, z; (ii) x, y+1, z; (iii) −y+1, x−y+1, z; (iv) −x+y, −x+1, z; (v) y−2/3, −x+y+2/3, −z+2/3; (vi) −x+1/3, −y+5/3, −z+2/3; (vii) −x+1, −y+1, −z+1; (viii) x+1, y, z; (ix) x, y−1, z; (x) −x+4/3, −y+2/3, −z+2/3; (xi) −x+4/3, −y+5/3, −z+2/3; (xii) x−y+1/3, x+2/3, −z+2/3; (xiii) x−y+1/3, x−1/3, −z+2/3; (xiv) y−2/3, −x+y−1/3, −z+2/3; (xv) x−y+4/3, x+2/3, −z+2/3; (xvi) −x+2, −y+1, −z+1; (xvii) −x+1, −y, −z+1.

(Cu1p95Se_CVT1_365K) top

Crystal data top

0.33(Cu_5.83Se₃)	D_x = 6.714 Mg m⁻³
M_r = 202.86	Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3m	Cell parameters from 246 reflections
a = 4.1323 (10) Å	θ = 3.0–27.1°
c = 20.358 (9) Å	µ = 38.29 mm⁻¹
V = 301.1 (2) Å³	T = 365 K
Z = 6	Irregular, metallic grayish gray
F(000) = 543	0.09 × 0.05 × 0.02 mm

Data collection top

SuperNova, Single source at offset, Atlas diffractometer	97 reflections with I > 2σ(I)
Detector resolution: 10.3590 pixels mm^-1	R_int = 0.053
ω scans	θ_max = 26.2°, θ_min = 3.0°
Absorption correction: multi-scan CrysAlisPro 1.171.38.41 (Rigaku Oxford Diffraction, 2015) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	h = −4→5
T_min = 0.201, T_max = 1.000	k = −5→5
772 measured reflections	l = −24→24
102 independent reflections

Refinement top

Refinement on F²	19 parameters
Least-squares matrix: full	1 restraint
R[F² > 2σ(F²)] = 0.100	w = 1/[σ²(F_o²) + (0.2P)²] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.278	(Δ/σ)_max < 0.001
S = 1.39	Δρ_max = 2.23 e Å⁻³
102 reflections	Δρ_min = −2.68 e Å⁻³

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Se1	0.3333	0.6667	0.42128 (15)	0.0411 (19)
Cu1B	0.6667	0.3333	0.409 (2)	0.094 (13)	0.43 (4)
Cu2	0.387 (2)	0.775 (4)	0.3018 (6)	0.098 (7)	0.329 (6)
Cu1A	0.6667	0.3333	0.4576 (11)	0.074 (5)	0.52 (4)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Se1	0.035 (2)	0.035 (2)	0.053 (3)	0.0176 (11)	0.000	0.000
Cu1B	0.047 (5)	0.047 (5)	0.19 (4)	0.023 (3)	0.000	0.000
Cu2	0.090 (7)	0.108 (14)	0.103 (8)	0.054 (7)	0.024 (4)	0.048 (8)
Cu1A	0.076 (6)	0.076 (6)	0.071 (11)	0.038 (3)	0.000	0.000

Geometric parameters (Å, º) top

Se1—Cu1Bⁱ	2.399 (5)	Cu2—Cu2^xii	2.900 (13)
Se1—Cu1Bⁱⁱ	2.399 (5)	Cu2—Cu2ⁱⁱⁱ	2.467 (14)
Se1—Cu1B	2.400 (5)	Cu2—Cu2^v	2.375 (19)
Se1—Cu2ⁱⁱⁱ	2.498 (7)	Cu2—Cu2^xiii	2.900 (13)
Se1—Cu2	2.462 (13)	Cu2—Cu2^xiv	2.900 (13)
Se1—Cu2^iv	2.462 (13)	Cu2—Cu2^vii	0.67 (2)
Se1—Cu2^v	2.498 (7)	Cu2—Cu2^iv	0.67 (2)
Se1—Cu2^vi	2.498 (7)	Cu2—Cu2^xi	2.467 (14)
Se1—Cu2^vii	2.462 (13)	Cu2—Cu2^vi	2.375 (19)
Se1—Cu1A^viii	2.47 (2)	Cu1A—Se1^viii	2.47 (2)
Se1—Cu1Aⁱ	2.497 (7)	Cu1A—Se1^ix	2.497 (7)
Se1—Cu1Aⁱⁱ	2.497 (7)	Cu1A—Se1^x	2.497 (7)
Cu1B—Se1^ix	2.399 (5)	Cu1A—Cu1A^xv	2.95 (3)
Cu1B—Se1^x	2.399 (5)	Cu1A—Cu1A^xvi	2.95 (3)
Cu2—Se1ⁱⁱⁱ	2.498 (7)	Cu1A—Cu1A^viii	2.95 (3)
Cu2—Se1^xi	2.498 (7)

Cu1Bⁱ—Se1—Cu1Bⁱⁱ	118.9 (4)	Cu2^iv—Cu2—Cu2^v	89.998 (13)
Cu1Bⁱ—Se1—Cu1B	118.9 (4)	Cu2^vii—Cu2—Cu2^xii	34.1 (4)
Cu1Bⁱⁱ—Se1—Cu1B	118.9 (4)	Cu2^xi—Cu2—Cu2^xiii	11.0 (5)
Cu2^vii—Se1—Cu2^vi	59.7 (3)	Cu2^vi—Cu2—Cu2ⁱⁱⁱ	15.8 (6)
Cu2^vi—Se1—Cu2ⁱⁱⁱ	15.4 (6)	Cu2^vii—Cu2—Cu2^xiv	83.4 (2)
Cu2^iv—Se1—Cu2^vi	71.5 (3)	Cu2ⁱⁱⁱ—Cu2—Cu2^xiv	11.0 (5)
Cu2—Se1—Cu2^vi	57.2 (4)	Cu2^vii—Cu2—Cu2^v	136.8 (4)
Cu2^vii—Se1—Cu2^v	71.5 (3)	Cu2^xiv—Cu2—Cu2^xii	90.9 (5)
Cu2^vii—Se1—Cu2^iv	15.6 (6)	Cu2ⁱⁱⁱ—Cu2—Cu2^xiii	113.9 (10)
Cu2^iv—Se1—Cu2ⁱⁱⁱ	71.5 (3)	Cu2^vi—Cu2—Cu2^xi	105.0 (9)
Cu2—Se1—Cu2^iv	15.6 (6)	Cu2^vii—Cu2—Cu2^vi	90.000 (11)
Cu2ⁱⁱⁱ—Se1—Cu2^v	100.5 (4)	Cu2^vii—Cu2—Cu2^iv	59.999 (3)
Cu2^vi—Se1—Cu2^v	87.7 (7)	Cu2^iv—Cu2—Cu2^xiv	135.4 (3)
Cu2^iv—Se1—Cu2^v	59.7 (3)	Cu2^vii—Cu2—Cu2^xi	124.5 (6)
Cu2^vii—Se1—Cu2ⁱⁱⁱ	57.2 (4)	Cu2^iv—Cu2—Cu2^vi	136.8 (4)
Cu2^vii—Se1—Cu2	15.6 (6)	Cu2^xi—Cu2—Cu2ⁱⁱⁱ	113.7 (10)
Cu2—Se1—Cu2ⁱⁱⁱ	59.7 (3)	Cu2^iv—Cu2—Cu2^xi	74.2 (6)
Cu2—Se1—Cu2^v	57.2 (4)	Cu2^v—Cu2—Cu2^xi	15.8 (6)
Cu1A^viii—Se1—Cu1Aⁱⁱ	72.8 (5)	Cu2^xiii—Cu2—Cu2^xiv	111.8 (8)
Cu1A^viii—Se1—Cu1Aⁱ	72.8 (5)	Cu2^vii—Cu2—Cu2^xiii	135.4 (3)
Cu1Aⁱ—Se1—Cu1Aⁱⁱ	111.7 (5)	Cu2^iv—Cu2—Cu2^xii	44.6 (3)
Se1^x—Cu1B—Se1	118.9 (4)	Cu2^v—Cu2—Cu2^xii	102.7 (7)
Se1^ix—Cu1B—Se1	118.9 (4)	Cu2^vi—Cu2—Cu2^xii	92.9 (6)
Se1^ix—Cu1B—Se1^x	118.9 (4)	Cu2^iv—Cu2—Cu2^xiii	83.4 (2)
Se1—Cu2—Se1ⁱⁱⁱ	120.3 (3)	Cu2^xi—Cu2—Cu2^xii	91.0 (6)
Se1—Cu2—Se1^xi	120.3 (3)	Cu2ⁱⁱⁱ—Cu2—Cu2^xii	79.9 (8)
Se1ⁱⁱⁱ—Cu2—Se1^xi	111.6 (5)	Cu2^v—Cu2—Cu2^vi	93.6 (7)
Se1—Cu2—Cu2^xii	54.8 (5)	Cu2^v—Cu2—Cu2^xiii	9.1 (3)
Se1—Cu2—Cu2^xi	60.9 (5)	Cu2^xiii—Cu2—Cu2^xii	101.9 (6)
Se1—Cu2—Cu2^xiv	67.5 (5)	Cu2^iv—Cu2—Cu2ⁱⁱⁱ	124.5 (6)
Se1ⁱⁱⁱ—Cu2—Cu2^xiv	53.65 (19)	Cu2^vi—Cu2—Cu2^xiv	9.1 (3)
Se1—Cu2—Cu2ⁱⁱⁱ	60.9 (5)	Cu2^vi—Cu2—Cu2^xiii	102.7 (7)
Se1^xi—Cu2—Cu2^xiii	53.65 (19)	Cu2^xi—Cu2—Cu2^xiv	113.9 (10)
Se1^xi—Cu2—Cu2^xiv	141.0 (5)	Cu2^vii—Cu2—Cu2ⁱⁱⁱ	74.2 (6)
Se1^xi—Cu2—Cu2^xii	125.87 (11)	Se1^viii—Cu1A—Se1^ix	107.2 (5)
Se1—Cu2—Cu2^xiii	67.5 (5)	Se1^ix—Cu1A—Se1^x	111.7 (5)
Se1ⁱⁱⁱ—Cu2—Cu2^xiii	141.0 (5)	Se1^viii—Cu1A—Se1^x	107.2 (5)
Se1ⁱⁱⁱ—Cu2—Cu2^xii	113.3 (5)	Se1^ix—Cu1A—Se1	111.6 (5)
Cu2^iv—Cu2—Se1ⁱⁱⁱ	133.9 (3)	Se1^viii—Cu1A—Se1	107.2 (5)
Cu2ⁱⁱⁱ—Cu2—Se1^xi	151.3 (10)	Se1^x—Cu1A—Se1	111.6 (5)
Cu2^iv—Cu2—Se1	82.2 (3)	Se1^viii—Cu1A—Cu1A^xv	54.1 (7)
Cu2^iv—Cu2—Se1^xi	82.3 (3)	Se1—Cu1A—Cu1A^viii	53.1 (2)
Cu2^vii—Cu2—Se1ⁱⁱⁱ	82.3 (3)	Se1^ix—Cu1A—Cu1A^viii	124.1 (3)
Cu2^vi—Cu2—Se1	62.2 (5)	Se1^ix—Cu1A—Cu1A^xv	53.1 (2)
Cu2^v—Cu2—Se1	62.2 (5)	Se1^viii—Cu1A—Cu1A^viii	54.1 (7)
Cu2^v—Cu2—Se1^xi	60.6 (4)	Se1^viii—Cu1A—Cu1A^xvi	54.1 (7)
Cu2ⁱⁱⁱ—Cu2—Se1ⁱⁱⁱ	59.5 (3)	Se1^x—Cu1A—Cu1A^viii	124.1 (3)
Cu2^xi—Cu2—Se1ⁱⁱⁱ	151.3 (10)	Se1—Cu1A—Cu1A^xvi	124.1 (3)
Cu2^vi—Cu2—Se1^xi	135.7 (3)	Se1^x—Cu1A—Cu1A^xv	124.1 (3)
Cu2^vii—Cu2—Se1^xi	133.9 (3)	Se1^ix—Cu1A—Cu1A^xvi	124.1 (3)
Cu2^vii—Cu2—Se1	82.2 (3)	Se1—Cu1A—Cu1A^xv	124.1 (3)
Cu2^xi—Cu2—Se1^xi	59.4 (3)	Se1^x—Cu1A—Cu1A^xvi	53.1 (2)
Cu2^vi—Cu2—Se1ⁱⁱⁱ	60.6 (4)	Cu1A^xv—Cu1A—Cu1A^xvi	89.1 (10)
Cu2^v—Cu2—Se1ⁱⁱⁱ	135.7 (3)	Cu1A^xv—Cu1A—Cu1A^viii	89.1 (10)
Cu2^v—Cu2—Cu2ⁱⁱⁱ	105.0 (9)	Cu1A^xvi—Cu1A—Cu1A^viii	89.1 (10)
Cu2^v—Cu2—Cu2^xiv	102.7 (7)

Symmetry codes: (i) x, y+1, z; (ii) x−1, y, z; (iii) −x+1/3, −y+5/3, −z+2/3; (iv) −x+y, −x+1, z; (v) x−y+4/3, x+2/3, −z+2/3; (vi) y−2/3, −x+y+2/3, −z+2/3; (vii) −y+1, x−y+1, z; (viii) −x+1, −y+1, −z+1; (ix) x+1, y, z; (x) x, y−1, z; (xi) −x+4/3, −y+5/3, −z+2/3; (xii) x−y+1/3, x−1/3, −z+2/3; (xiii) y+1/3, −x+y+2/3, −z+2/3; (xiv) x−y+1/3, x+2/3, −z+2/3; (xv) −x+2, −y+1, −z+1; (xvi) −x+1, −y, −z+1.

(Cu1p95Se_CVT1_372K) top

Crystal data top

0.33(Cu_5.82Se₃)	D_x = 6.738 Mg m⁻³
M_r = 202.86	Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3m	Cell parameters from 330 reflections
a = 4.1327 (7) Å	θ = 3.0–27.1°
c = 20.281 (5) Å	µ = 38.43 mm⁻¹
V = 299.98 (13) Å³	T = 372 K
Z = 6	Irregular
F(000) = 543	0.09 × 0.05 × 0.02 mm

Data collection top

SuperNova, Single source at offset, Atlas diffractometer	96 reflections with I > 2σ(I)
Detector resolution: 10.3590 pixels mm^-1	R_int = 0.057
ω scans	θ_max = 26.2°, θ_min = 3.0°
Absorption correction: multi-scan CrysAlisPro 1.171.38.41 (Rigaku Oxford Diffraction, 2015) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	h = −5→5
T_min = 0.270, T_max = 1.000	k = −5→5
924 measured reflections	l = −24→24
102 independent reflections

Refinement top

Refinement on F²	19 parameters
Least-squares matrix: full	1 restraint
R[F² > 2σ(F²)] = 0.100	w = 1/[σ²(F_o²) + (0.2P)²] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.288	(Δ/σ)_max < 0.001
S = 1.43	Δρ_max = 2.27 e Å⁻³
102 reflections	Δρ_min = −2.36 e Å⁻³

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Se1	0.3333	0.6667	0.42007 (13)	0.044 (2)
Cu1B	0.6667	0.3333	0.411 (3)	0.106 (17)	0.36 (4)
Cu2	0.381 (3)	0.762 (6)	0.2995 (7)	0.112 (8)	0.329 (5)
Cu1A	0.6667	0.3333	0.4582 (11)	0.087 (5)	0.59 (4)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Se1	0.039 (2)	0.039 (2)	0.055 (3)	0.0193 (11)	0.000	0.000
Cu1B	0.047 (5)	0.047 (5)	0.22 (5)	0.024 (3)	0.000	0.000
Cu2	0.098 (7)	0.129 (18)	0.119 (8)	0.065 (9)	0.027 (5)	0.054 (10)
Cu1A	0.090 (7)	0.090 (7)	0.082 (10)	0.045 (3)	0.000	0.000

Geometric parameters (Å, º) top

Se1—Cu1Bⁱ	2.394 (5)	Cu2—Cu2^v	2.46 (2)
Se1—Cu1Bⁱⁱ	2.394 (5)	Cu2—Cu2^ix	2.532 (18)
Se1—Cu1B	2.394 (5)	Cu2—Cu2^vii	2.915 (17)
Se1—Cu2ⁱⁱⁱ	2.480 (9)	Cu2—Cu2^xiii	2.915 (17)
Se1—Cu2^iv	2.468 (14)	Cu2—Cu2^xiv	2.915 (17)
Se1—Cu2^v	2.480 (9)	Cu2—Cu2^viii	0.59 (3)
Se1—Cu2^vi	2.480 (9)	Cu2—Cu2ⁱⁱⁱ	2.46 (2)
Se1—Cu2	2.468 (14)	Cu2—Cu2^vi	2.532 (18)
Se1—Cu2^vii	2.480 (9)	Cu2—Cu2^iv	0.59 (3)
Se1—Cu2^viii	2.468 (14)	Cu1A—Se1^x	2.47 (2)
Se1—Cu2^ix	2.480 (9)	Cu1A—Se1^xi	2.508 (7)
Se1—Cu1A^x	2.47 (2)	Cu1A—Se1^xii	2.508 (7)
Cu1B—Se1^xi	2.394 (5)	Cu1A—Cu1A^xv	2.93 (3)
Cu1B—Se1^xii	2.394 (5)	Cu1A—Cu1A^x	2.93 (3)
Cu2—Se1^ix	2.480 (9)	Cu1A—Cu1A^xvi	2.93 (3)
Cu2—Se1^vi	2.480 (9)

Cu1Bⁱ—Se1—Cu1Bⁱⁱ	119.4 (4)	Cu2^viii—Cu2—Se1^vi	83.2 (4)
Cu1Bⁱ—Se1—Cu1B	119.3 (4)	Cu2^iv—Cu2—Se1^vi	135.6 (4)
Cu1Bⁱⁱ—Se1—Cu1B	119.3 (4)	Cu2^v—Cu2—Se1	60.4 (6)
Cu2—Se1—Cu2^ix	61.6 (4)	Cu2^vii—Cu2—Cu2^xiii	11.6 (6)
Cu2^iv—Se1—Cu2^vii	61.6 (4)	Cu2^ix—Cu2—Cu2^xiii	80.8 (11)
Cu2ⁱⁱⁱ—Se1—Cu2^v	91.2 (9)	Cu2^viii—Cu2—Cu2^xiii	44.9 (3)
Cu2^v—Se1—Cu2^ix	13.6 (8)	Cu2ⁱⁱⁱ—Cu2—Cu2^v	92.0 (8)
Cu2—Se1—Cu2^viii	13.7 (8)	Cu2^viii—Cu2—Cu2^v	136.0 (4)
Cu2—Se1—Cu2^vii	72.2 (4)	Cu2^viii—Cu2—Cu2ⁱⁱⁱ	90.000 (13)
Cu2—Se1—Cu2^iv	13.7 (8)	Cu2^viii—Cu2—Cu2^iv	60.001 (3)
Cu2^vi—Se1—Cu2^vii	91.2 (9)	Cu2^iv—Cu2—Cu2ⁱⁱⁱ	136.0 (4)
Cu2^viii—Se1—Cu2^iv	13.7 (8)	Cu2ⁱⁱⁱ—Cu2—Cu2^vi	13.5 (9)
Cu2ⁱⁱⁱ—Se1—Cu2^ix	102.6 (4)	Cu2^vi—Cu2—Cu2^ix	109.4 (11)
Cu2—Se1—Cu2ⁱⁱⁱ	59.7 (5)	Cu2^ix—Cu2—Cu2^vii	90.3 (8)
Cu2^iv—Se1—Cu2^v	61.6 (4)	Cu2^viii—Cu2—Cu2^xiv	84.2 (3)
Cu2^viii—Se1—Cu2ⁱⁱⁱ	61.6 (4)	Cu2ⁱⁱⁱ—Cu2—Cu2^xiii	100.1 (8)
Cu2^vi—Se1—Cu2^v	102.6 (4)	Cu2^iv—Cu2—Cu2^xiv	135.1 (3)
Cu2^iv—Se1—Cu2ⁱⁱⁱ	72.2 (4)	Cu2^iv—Cu2—Cu2^ix	76.5 (9)
Cu2^viii—Se1—Cu2^vii	59.7 (5)	Cu2ⁱⁱⁱ—Cu2—Cu2^xiv	8.1 (5)
Cu2—Se1—Cu2^vi	61.6 (4)	Cu2^v—Cu2—Cu2^vii	100.1 (8)
Cu2ⁱⁱⁱ—Se1—Cu2^vii	102.6 (4)	Cu2^v—Cu2—Cu2^xiv	100.1 (8)
Cu2^viii—Se1—Cu2^vi	59.7 (5)	Cu2^v—Cu2—Cu2^vi	101.6 (9)
Cu2^v—Se1—Cu2^vii	112.9 (6)	Cu2^viii—Cu2—Cu2^vi	76.5 (9)
Cu2^iv—Se1—Cu2^vi	72.2 (4)	Cu2^iv—Cu2—Cu2^v	90.00 (2)
Cu2^iv—Se1—Cu2^ix	59.7 (5)	Cu2^xiv—Cu2—Cu2^xiii	99.7 (6)
Cu2ⁱⁱⁱ—Se1—Cu2^vi	13.6 (8)	Cu2^xiv—Cu2—Cu2^vii	90.3 (7)
Cu2^vi—Se1—Cu2^ix	112.9 (6)	Cu2^iv—Cu2—Cu2^vi	125.7 (9)
Cu2—Se1—Cu2^v	59.7 (5)	Cu2^iv—Cu2—Cu2^xiii	35.9 (5)
Cu2^vii—Se1—Cu2^ix	102.6 (4)	Cu2^vi—Cu2—Cu2^xiv	9.4 (6)
Cu2^viii—Se1—Cu2^v	72.2 (4)	Cu2^v—Cu2—Cu2^xiii	91.7 (7)
Cu2^viii—Se1—Cu2^ix	72.2 (4)	Cu2^ix—Cu2—Cu2^xiv	109.6 (11)
Se1^xi—Cu1B—Se1^xii	119.4 (4)	Cu2^viii—Cu2—Cu2^ix	125.7 (9)
Se1^xi—Cu1B—Se1	119.3 (4)	Cu2^viii—Cu2—Cu2^vii	35.9 (5)
Se1^xii—Cu1B—Se1	119.3 (4)	Cu2^vi—Cu2—Cu2^xiii	90.3 (7)
Se1—Cu2—Se1^vi	118.4 (4)	Cu2^iv—Cu2—Cu2^vii	44.9 (3)
Se1—Cu2—Se1^ix	118.4 (4)	Cu2ⁱⁱⁱ—Cu2—Cu2^ix	101.6 (9)
Se1^vi—Cu2—Se1^ix	112.9 (6)	Cu2ⁱⁱⁱ—Cu2—Cu2^vii	91.7 (7)
Se1^vi—Cu2—Cu2^xiv	53.7 (2)	Cu2^v—Cu2—Cu2^ix	13.5 (9)
Se1^ix—Cu2—Cu2^ix	59.0 (4)	Cu2^vi—Cu2—Cu2^vii	80.8 (11)
Se1^vi—Cu2—Cu2^xiii	126.11 (10)	Se1^x—Cu1A—Se1^xi	108.0 (5)
Se1—Cu2—Cu2^vii	54.1 (5)	Se1^xi—Cu1A—Se1	110.9 (5)
Se1—Cu2—Cu2^xiv	65.3 (6)	Se1^x—Cu1A—Se1	108.0 (5)
Se1^ix—Cu2—Cu2^vii	126.10 (10)	Se1^x—Cu1A—Se1^xii	108.0 (5)
Se1^ix—Cu2—Cu2^xiv	139.3 (7)	Se1^xi—Cu1A—Se1^xii	110.9 (5)
Se1—Cu2—Cu2^vi	59.4 (5)	Se1^xii—Cu1A—Se1	110.9 (5)
Se1^vi—Cu2—Cu2^vii	114.9 (7)	Se1—Cu1A—Cu1A^xvi	124.5 (3)
Se1^ix—Cu2—Cu2^vi	147.6 (13)	Se1^xi—Cu1A—Cu1A^xvi	124.5 (3)
Se1—Cu2—Cu2^xiii	54.1 (5)	Se1—Cu1A—Cu1A^xv	124.5 (3)
Se1—Cu2—Cu2^ix	59.4 (5)	Se1^xi—Cu1A—Cu1A^x	124.5 (3)
Se1^ix—Cu2—Cu2^xiii	114.9 (7)	Se1^xii—Cu1A—Cu1A^xvi	53.4 (2)
Se1^vi—Cu2—Cu2^ix	147.6 (13)	Se1—Cu1A—Cu1A^x	53.3 (2)
Se1^vi—Cu2—Cu2^vi	59.0 (4)	Se1^x—Cu1A—Cu1A^x	54.6 (7)
Cu2^v—Cu2—Se1^ix	59.9 (5)	Se1^x—Cu1A—Cu1A^xv	54.6 (7)
Cu2ⁱⁱⁱ—Cu2—Se1^ix	134.2 (4)	Se1^xii—Cu1A—Cu1A^x	124.5 (3)
Cu2ⁱⁱⁱ—Cu2—Se1^vi	59.9 (5)	Se1^xi—Cu1A—Cu1A^xv	53.4 (2)
Cu2^viii—Cu2—Se1	83.1 (4)	Se1^xii—Cu1A—Cu1A^xv	124.5 (3)
Cu2^iv—Cu2—Se1^ix	83.2 (4)	Se1^x—Cu1A—Cu1A^xvi	54.6 (7)
Cu2^iv—Cu2—Se1	83.2 (4)	Cu1A^xv—Cu1A—Cu1A^xvi	89.8 (10)
Cu2^v—Cu2—Se1^vi	134.2 (4)	Cu1A^xvi—Cu1A—Cu1A^x	89.8 (10)
Cu2ⁱⁱⁱ—Cu2—Se1	60.4 (6)	Cu1A^xv—Cu1A—Cu1A^x	89.8 (10)
Cu2^viii—Cu2—Se1^ix	135.6 (4)

Symmetry codes: (i) x, y+1, z; (ii) x−1, y, z; (iii) y−2/3, −x+y+2/3, −z+2/3; (iv) −x+y, −x+1, z; (v) x−y+4/3, x+2/3, −z+2/3; (vi) −x+1/3, −y+5/3, −z+2/3; (vii) x−y+1/3, x−1/3, −z+2/3; (viii) −y+1, x−y+1, z; (ix) −x+4/3, −y+5/3, −z+2/3; (x) −x+1, −y+1, −z+1; (xi) x+1, y, z; (xii) x, y−1, z; (xiii) y−2/3, −x+y−1/3, −z+2/3; (xiv) x−y+1/3, x+2/3, −z+2/3; (xv) −x+2, −y+1, −z+1; (xvi) −x+1, −y, −z+1.

(Cu1p95Se_CVT1_380K) top

Crystal data top

0.02(Cu₉₆)·1(Se)	Mo Kα radiation, λ = 0.71073 Å
M_r = 202.86	Cell parameters from 272 reflections
Cubic, Fm3m	θ = 6.0–27.8°
a = 5.8449 (2) Å	µ = 38.48 mm⁻¹
V = 199.68 (2) Å³	T = 380 K
Z = 4	Irregular
F(000) = 362	0.09 × 0.05 × 0.02 mm
D_x = 6.748 Mg m⁻³

Data collection top

SuperNova, Single source at offset, Atlas diffractometer	22 reflections with I > 2σ(I)
Detector resolution: 10.3590 pixels mm^-1	R_int = 0.087
ω scans	θ_max = 26.0°, θ_min = 6.1°
Absorption correction: multi-scan CrysAlisPro 1.171.38.41 (Rigaku Oxford Diffraction, 2015) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	h = −6→6
T_min = 0.225, T_max = 1.000	k = −7→7
380 measured reflections	l = −7→7
22 independent reflections

Refinement top

Refinement on F²	6 parameters
Least-squares matrix: full	1 restraint
R[F² > 2σ(F²)] = 0.048	w = 1/[σ²(F_o²) + (0.0353P)² + 13.765P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.106	(Δ/σ)_max < 0.001
S = 1.35	Δρ_max = 1.30 e Å⁻³
22 reflections	Δρ_min = −0.68 e Å⁻³

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Cu1	0.2500	0.2500	0.2500	0.066 (4)	0.61 (2)
Se2	0.0000	0.0000	0.0000	0.0376 (19)
Cu2	0.338 (4)	0.338 (4)	0.338 (4)	0.066 (4)	0.091 (6)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cu1	0.066 (4)	0.066 (4)	0.066 (4)	0.000	0.000	0.000
Se2	0.0376 (19)	0.0376 (19)	0.0376 (19)	0.000	0.000	0.000
Cu2	0.066 (4)	0.066 (4)	0.066 (4)	0.000	0.000	0.000

Geometric parameters (Å, º) top

Cu1—Cu1ⁱ	2.9224 (1)	Cu2—Cu2^viii	2.68 (6)
Cu1—Cu1ⁱⁱ	2.9224 (1)	Cu2—Cu2^ix	2.68 (6)
Cu1—Cu1ⁱⁱⁱ	2.9224 (1)	Cu2—Cu2^x	2.68 (6)
Cu1—Cu1^iv	2.9224 (1)	Cu2—Cu2^xi	1.46 (6)
Cu1—Cu1^v	2.9224 (1)	Cu2—Cu2ⁱⁱ	2.388 (3)
Cu1—Cu1^vi	2.9224 (1)	Cu2—Cu2^xii	1.46 (6)
Cu2—Cu2ⁱ	2.388 (3)	Cu2—Cu2^xiii	1.89 (4)
Cu2—Cu2^vii	1.89 (4)	Cu2—Cu2^xiv	1.46 (6)
Cu2—Cu2^iv	2.388 (3)	Cu2—Cu2^xv	1.89 (4)

Cu1ⁱ—Cu1—Cu1ⁱⁱⁱ	90.0	Cu2^iv—Cu2—Cu2^ix	75.2 (15)
Cu1^v—Cu1—Cu1^iv	180.0	Cu2^xi—Cu2—Cu2^xiii	135.000 (3)
Cu1^v—Cu1—Cu1^vi	90.0	Cu2ⁱ—Cu2—Cu2^viii	127.5 (18)
Cu1ⁱⁱ—Cu1—Cu1^iv	90.0	Cu2^xii—Cu2—Cu2^xiii	135.000 (1)
Cu1ⁱⁱⁱ—Cu1—Cu1^vi	90.0	Cu2^xiv—Cu2—Cu2^x	120.0
Cu1ⁱⁱ—Cu1—Cu1^vi	90.0	Cu2^xiv—Cu2—Cu2^xiii	90.000 (6)
Cu1ⁱ—Cu1—Cu1^v	90.0	Cu2^vii—Cu2—Cu2^iv	115.5 (11)
Cu1ⁱ—Cu1—Cu1ⁱⁱ	90.0	Cu2^xv—Cu2—Cu2^xiii	90.001 (4)
Cu1ⁱⁱⁱ—Cu1—Cu1^v	90.0	Cu2ⁱⁱ—Cu2—Cu2^x	75.2 (15)
Cu1ⁱ—Cu1—Cu1^vi	180.0	Cu2^xi—Cu2—Cu2^vii	135.0
Cu1ⁱⁱ—Cu1—Cu1^v	90.0	Cu2^xii—Cu2—Cu2^viii	180 (3)
Cu1ⁱⁱⁱ—Cu1—Cu1ⁱⁱ	180.0	Cu2^xii—Cu2—Cu2^vii	90.000 (2)
Cu1ⁱ—Cu1—Cu1^iv	90.0	Cu2^ix—Cu2—Cu2^x	60.000 (1)
Cu1ⁱⁱⁱ—Cu1—Cu1^iv	90.0	Cu2^xiv—Cu2—Cu2^vii	135.0
Cu1^iv—Cu1—Cu1^vi	90.0	Cu2^vii—Cu2—Cu2^viii	90.001 (3)
Cu2^xii—Cu2—Cu2^ix	120.000 (2)	Cu2^xv—Cu2—Cu2^vii	90.001 (3)
Cu2^xiii—Cu2—Cu2^iv	115.5 (11)	Cu2ⁱⁱ—Cu2—Cu2ⁱ	119.8 (2)
Cu2^xiii—Cu2—Cu2^viii	45.000 (1)	Cu2^xiii—Cu2—Cu2^vii	90.001 (2)
Cu2^vii—Cu2—Cu2^ix	45.000 (1)	Cu2^xii—Cu2—Cu2^iv	104.8 (15)
Cu2^xi—Cu2—Cu2^viii	120.0	Cu2^xi—Cu2—Cu2ⁱⁱ	104.8 (15)
Cu2^viii—Cu2—Cu2^ix	60.000 (2)	Cu2^xiv—Cu2—Cu2^ix	180 (3)
Cu2^iv—Cu2—Cu2^viii	75.2 (15)	Cu2^xii—Cu2—Cu2ⁱⁱ	104.8 (15)
Cu2^xv—Cu2—Cu2^x	90.001 (4)	Cu2^xi—Cu2—Cu2^xii	59.999 (4)
Cu2ⁱⁱ—Cu2—Cu2^iv	119.8 (2)	Cu2^xiv—Cu2—Cu2ⁱⁱ	52.5 (18)
Cu2ⁱ—Cu2—Cu2^x	75.2 (15)	Cu2ⁱⁱ—Cu2—Cu2^ix	127.5 (18)
Cu2^xiv—Cu2—Cu2^viii	120.000 (2)	Cu2^xv—Cu2—Cu2ⁱⁱ	115.5 (11)
Cu2^xiii—Cu2—Cu2ⁱ	115.5 (11)	Cu2^xi—Cu2—Cu2^xiv	59.999 (1)
Cu2ⁱⁱ—Cu2—Cu2^viii	75.2 (15)	Cu2^xiii—Cu2—Cu2ⁱⁱ	37.5 (18)
Cu2^xi—Cu2—Cu2^iv	52.5 (18)	Cu2^xi—Cu2—Cu2^x	180.0 (18)
Cu2^xiv—Cu2—Cu2^iv	104.8 (15)	Cu2^vii—Cu2—Cu2ⁱⁱ	115.5 (11)
Cu2^xv—Cu2—Cu2^ix	45.0	Cu2^xii—Cu2—Cu2^xiv	59.999 (1)
Cu2^xi—Cu2—Cu2^ix	120.000 (2)	Cu2^xi—Cu2—Cu2ⁱ	104.8 (15)
Cu2ⁱ—Cu2—Cu2^ix	75.2 (15)	Cu2^xiii—Cu2—Cu2^x	45.0
Cu2^xv—Cu2—Cu2^iv	37.5 (18)	Cu2^xii—Cu2—Cu2ⁱ	52.5 (18)
Cu2^xii—Cu2—Cu2^x	120.000 (1)	Cu2^xi—Cu2—Cu2^xv	90.000 (1)
Cu2^xv—Cu2—Cu2^viii	45.000 (2)	Cu2^xiv—Cu2—Cu2ⁱ	104.8 (15)
Cu2^vii—Cu2—Cu2^x	45.000 (1)	Cu2^iv—Cu2—Cu2^x	127.5 (18)
Cu2^xiii—Cu2—Cu2^ix	90.001 (5)	Cu2^xv—Cu2—Cu2ⁱ	115.5 (11)
Cu2^viii—Cu2—Cu2^x	60.000 (1)	Cu2^xii—Cu2—Cu2^xv	135.000 (1)
Cu2ⁱ—Cu2—Cu2^iv	119.8 (2)	Cu2^vii—Cu2—Cu2ⁱ	37.5 (18)
Cu2^xiv—Cu2—Cu2^xv	135.000 (1)

Symmetry codes: (i) −x+1/2, −y+1/2, −z+1; (ii) −x+1, −y+1/2, −z+1/2; (iii) −x, −y+1/2, −z+1/2; (iv) −x+1/2, −y+1, −z+1/2; (v) −x+1/2, −y, −z+1/2; (vi) −x+1/2, −y+1/2, −z; (vii) x, y, −z+1; (viii) −x+1, −y+1, z; (ix) y, −x+1, −z+1; (x) −y+1, x, −z+1; (xi) −y+1/2, x, −z+1/2; (xii) −x+1/2, −y+1/2, z; (xiii) −y+1, x, z; (xiv) y, −x+1/2, −z+1/2; (xv) y, −x+1, z.

(Cu1p95Se_CVT1_400K) top

Crystal data top

0.06(Cu₃₂)·1(Se)	Mo Kα radiation, λ = 0.71073 Å
M_r = 202.55	Cell parameters from 163 reflections
Cubic, Fm3m	θ = 6.0–24.9°
a = 5.8538 (3) Å	µ = 38.26 mm⁻¹
V = 200.59 (3) Å³	T = 400 K
Z = 4	Irregular
F(000) = 362	0.09 × 0.05 × 0.02 mm
D_x = 6.707 Mg m⁻³

Data collection top

SuperNova, Single source at offset, Atlas diffractometer	22 reflections with I > 2σ(I)
Detector resolution: 10.3590 pixels mm^-1	R_int = 0.079
ω scans	θ_max = 26.0°, θ_min = 6.0°
Absorption correction: multi-scan CrysAlisPro 1.171.38.41 (Rigaku Oxford Diffraction, 2015) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	h = −7→7
T_min = 0.321, T_max = 1.000	k = −7→7
277 measured reflections	l = −5→7
22 independent reflections

Refinement top

Refinement on F²	6 parameters
Least-squares matrix: full	1 restraint
R[F² > 2σ(F²)] = 0.043	w = 1/[σ²(F_o²) + 16.3542P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.087	(Δ/σ)_max < 0.001
S = 1.29	Δρ_max = 0.50 e Å⁻³
22 reflections	Δρ_min = −0.91 e Å⁻³

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Cu1	0.2500	0.2500	0.2500	0.071 (4)	0.61 (2)
Se	0.0000	0.0000	0.0000	0.0423 (19)
Cu2	0.339 (4)	0.339 (4)	0.339 (4)	0.071 (4)	0.091 (6)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cu1	0.071 (4)	0.071 (4)	0.071 (4)	0.000	0.000	0.000
Se	0.0423 (19)	0.0423 (19)	0.0423 (19)	0.000	0.000	0.000
Cu2	0.071 (4)	0.071 (4)	0.071 (4)	0.000	0.000	0.000

Geometric parameters (Å, º) top

Cu1—Cu1ⁱ	2.9269 (2)	Cu2—Cu2^viii	2.67 (6)
Cu1—Cu1ⁱⁱ	2.9269 (2)	Cu2—Cu2^ix	2.67 (6)
Cu1—Cu1ⁱⁱⁱ	2.9269 (2)	Cu2—Cu2^x	2.67 (6)
Cu1—Cu1^iv	2.9269 (2)	Cu2—Cu2^xi	1.47 (6)
Cu1—Cu1^v	2.9269 (2)	Cu2—Cu2ⁱ	2.392 (4)
Cu1—Cu1^vi	2.9269 (2)	Cu2—Cu2^xii	1.47 (6)
Cu2—Cu2ⁱⁱ	2.392 (4)	Cu2—Cu2^xiii	1.89 (4)
Cu2—Cu2^vii	1.89 (4)	Cu2—Cu2^xiv	1.47 (6)
Cu2—Cu2^iv	2.392 (3)	Cu2—Cu2^xv	1.89 (4)

Cu1ⁱ—Cu1—Cu1ⁱⁱⁱ	90.0	Cu2^iv—Cu2—Cu2^ix	75.5 (15)
Cu1^v—Cu1—Cu1^iv	180.0	Cu2^xi—Cu2—Cu2^xiii	135.000 (1)
Cu1^v—Cu1—Cu1^vi	90.0	Cu2ⁱⁱ—Cu2—Cu2^viii	75.5 (15)
Cu1ⁱⁱ—Cu1—Cu1^iv	90.0	Cu2^xii—Cu2—Cu2^xiii	90.000 (1)
Cu1ⁱⁱⁱ—Cu1—Cu1^vi	90.0	Cu2^xiv—Cu2—Cu2^x	120.000 (1)
Cu1ⁱⁱ—Cu1—Cu1^vi	90.0	Cu2^xiv—Cu2—Cu2^xiii	135.000 (1)
Cu1ⁱ—Cu1—Cu1^v	90.0	Cu2^vii—Cu2—Cu2^iv	115.8 (11)
Cu1ⁱ—Cu1—Cu1ⁱⁱ	90.0	Cu2^xv—Cu2—Cu2^xiii	90.001 (1)
Cu1ⁱⁱⁱ—Cu1—Cu1^v	90.0	Cu2ⁱ—Cu2—Cu2^x	75.5 (15)
Cu1ⁱ—Cu1—Cu1^vi	180.0	Cu2^xi—Cu2—Cu2^vii	135.000 (3)
Cu1ⁱⁱ—Cu1—Cu1^v	90.0	Cu2^xii—Cu2—Cu2^viii	120.000 (1)
Cu1ⁱⁱⁱ—Cu1—Cu1ⁱⁱ	180.0	Cu2^xii—Cu2—Cu2^vii	135.0
Cu1ⁱ—Cu1—Cu1^iv	90.0	Cu2^ix—Cu2—Cu2^x	60.001 (2)
Cu1ⁱⁱⁱ—Cu1—Cu1^iv	90.0	Cu2^xiv—Cu2—Cu2^vii	90.000 (3)
Cu1^iv—Cu1—Cu1^vi	90.0	Cu2^vii—Cu2—Cu2^viii	90.0
Cu2^xii—Cu2—Cu2^ix	120.000 (2)	Cu2^xv—Cu2—Cu2^vii	90.0
Cu2^xiii—Cu2—Cu2^iv	38.0 (18)	Cu2ⁱ—Cu2—Cu2ⁱⁱ	119.8 (3)
Cu2^xiii—Cu2—Cu2^viii	45.000 (2)	Cu2^xiii—Cu2—Cu2^vii	90.0
Cu2^vii—Cu2—Cu2^ix	45.0	Cu2^xii—Cu2—Cu2^iv	52.0 (18)
Cu2^xi—Cu2—Cu2^viii	120.000 (2)	Cu2^xi—Cu2—Cu2ⁱ	104.5 (15)
Cu2^viii—Cu2—Cu2^ix	60.001 (1)	Cu2^xiv—Cu2—Cu2^ix	120.000 (2)
Cu2^iv—Cu2—Cu2^viii	75.5 (15)	Cu2^xii—Cu2—Cu2ⁱ	104.5 (15)
Cu2^xv—Cu2—Cu2^x	45.0	Cu2^xi—Cu2—Cu2^xii	59.999 (3)
Cu2ⁱ—Cu2—Cu2^iv	119.8 (3)	Cu2^xiv—Cu2—Cu2ⁱ	52.0 (18)
Cu2ⁱⁱ—Cu2—Cu2^x	75.5 (15)	Cu2ⁱ—Cu2—Cu2^ix	75.5 (15)
Cu2^xiv—Cu2—Cu2^viii	180.0 (12)	Cu2^xv—Cu2—Cu2ⁱ	115.8 (11)
Cu2^xiii—Cu2—Cu2ⁱⁱ	115.8 (11)	Cu2^xi—Cu2—Cu2^xiv	59.999 (3)
Cu2ⁱ—Cu2—Cu2^viii	128.0 (18)	Cu2^xiii—Cu2—Cu2ⁱ	115.8 (11)
Cu2^xi—Cu2—Cu2^iv	104.5 (15)	Cu2^xi—Cu2—Cu2^x	120.0
Cu2^xiv—Cu2—Cu2^iv	104.5 (15)	Cu2^vii—Cu2—Cu2ⁱ	38.0 (18)
Cu2^xv—Cu2—Cu2^ix	90.001 (2)	Cu2^xii—Cu2—Cu2^xiv	59.999 (1)
Cu2^xi—Cu2—Cu2^ix	180.0 (12)	Cu2^xi—Cu2—Cu2ⁱⁱ	52.0 (18)
Cu2ⁱⁱ—Cu2—Cu2^ix	128.0 (18)	Cu2^xiii—Cu2—Cu2^x	90.001 (1)
Cu2^xv—Cu2—Cu2^iv	115.8 (11)	Cu2^xii—Cu2—Cu2ⁱⁱ	104.5 (15)
Cu2^xii—Cu2—Cu2^x	180.0	Cu2^xi—Cu2—Cu2^xv	90.000 (5)
Cu2^xv—Cu2—Cu2^viii	45.000 (1)	Cu2^xiv—Cu2—Cu2ⁱⁱ	104.5 (15)
Cu2^vii—Cu2—Cu2^x	45.0	Cu2^iv—Cu2—Cu2^x	128.0 (18)
Cu2^xiii—Cu2—Cu2^ix	45.0	Cu2^xv—Cu2—Cu2ⁱⁱ	38.0 (18)
Cu2^viii—Cu2—Cu2^x	60.001 (2)	Cu2^xii—Cu2—Cu2^xv	135.0
Cu2ⁱⁱ—Cu2—Cu2^iv	119.8 (3)	Cu2^vii—Cu2—Cu2ⁱⁱ	115.8 (11)
Cu2^xiv—Cu2—Cu2^xv	135.000 (2)

Symmetry codes: (i) −x+1/2, −y+1/2, −z+1; (ii) −x+1, −y+1/2, −z+1/2; (iii) −x, −y+1/2, −z+1/2; (iv) −x+1/2, −y+1, −z+1/2; (v) −x+1/2, −y, −z+1/2; (vi) −x+1/2, −y+1/2, −z; (vii) x, y, −z+1; (viii) −x+1, −y+1, z; (ix) x, −y+1, −z+1; (x) −x+1, y, −z+1; (xi) x, −y+1/2, −z+1/2; (xii) −x+1/2, y, −z+1/2; (xiii) x, −y+1, z; (xiv) −x+1/2, −y+1/2, z; (xv) −x+1, y, z.

(Cu2-xSe_CVT2_100K_afterheatingto450K) top

Crystal data top

0.33(Cu_5.3Se₃)	D_x = 6.407 Mg m⁻³
M_r = 191.32	Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3m	Cell parameters from 429 reflections
a = 4.1017 (10) Å	θ = 3.0–27.9°
c = 20.420 (7) Å	µ = 36.85 mm⁻¹
V = 297.52 (18) Å³	T = 104 K
Z = 6	Irregular, metallic grayish gray
F(000) = 512	0.11 × 0.09 × 0.03 mm

Data collection top

SuperNova, Single source at offset, Atlas diffractometer	101 independent reflections
Radiation source: micro-focus sealed X-ray tube, SuperNova (Mo) X-ray Source	101 reflections with I > 2σ(I)
Mirror monochromator	R_int = 0.074
Detector resolution: 10.3590 pixels mm^-1	θ_max = 26.3°, θ_min = 3.0°
ω scans	h = −5→3
Absorption correction: multi-scan CrysAlisPro 1.171.38.41 (Rigaku Oxford Diffraction, 2015) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	k = −4→5
T_min = 0.487, T_max = 1.000	l = −24→23
683 measured reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Primary atom site location: structure-invariant direct methods
R[F² > 2σ(F²)] = 0.075	w = 1/[σ²(F_o²) + (0.0727P)² + 101.1774P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.216	(Δ/σ)_max < 0.001
S = 1.35	Δρ_max = 2.79 e Å⁻³
101 reflections	Δρ_min = −3.36 e Å⁻³
19 parameters

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Se01	0.3333	0.6667	0.4252 (2)	0.0196 (17)
Cu1B	0.6667	0.3333	0.4005 (7)	0.021 (5)	0.48 (4)
Cu2	0.4049 (17)	0.810 (3)	0.3078 (4)	0.034 (4)	0.305 (13)
Cu1A	0.6667	0.3333	0.4494 (15)	0.042 (10)	0.37 (4)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Se01	0.0195 (19)	0.0195 (19)	0.020 (3)	0.0097 (9)	0.000	0.000
Cu1B	0.021 (5)	0.021 (5)	0.022 (9)	0.010 (3)	0.000	0.000
Cu2	0.045 (6)	0.037 (7)	0.016 (4)	0.019 (4)	0.0009 (18)	0.002 (4)
Cu1A	0.024 (7)	0.024 (7)	0.08 (3)	0.012 (4)	0.000	0.000

Geometric parameters (Å, º) top

Se01—Cu1Bⁱ	2.421 (3)	Cu1B—Cu2^vii	2.654 (15)
Se01—Cu1Bⁱⁱ	2.421 (3)	Cu1B—Cu2^x	2.791 (9)
Se01—Cu1B	2.421 (3)	Cu1B—Cu2^xv	2.045 (13)
Se01—Cu2ⁱⁱⁱ	2.450 (9)	Cu2—Se01^vi	2.549 (6)
Se01—Cu2^iv	2.549 (6)	Cu2—Se01^xiv	2.549 (6)
Se01—Cu2	2.450 (9)	Cu2—Cu1B^xiv	2.045 (13)
Se01—Cu2^v	2.549 (6)	Cu2—Cu1Bⁱⁱ	2.654 (15)
Se01—Cu2^vi	2.549 (6)	Cu2—Cu2^vi	2.307 (8)
Se01—Cu2^vii	2.450 (9)	Cu2—Cu2ⁱⁱⁱ	0.88 (2)
Se01—Cu1Aⁱⁱ	2.419 (6)	Cu2—Cu2^vii	0.88 (2)
Se01—Cu1Aⁱ	2.419 (6)	Cu2—Cu2^v	2.132 (13)
Se01—Cu1A	2.419 (6)	Cu2—Cu2^xiv	2.307 (8)
Cu1B—Se01^viii	2.421 (3)	Cu2—Cu2^xvi	2.132 (13)
Cu1B—Se01^ix	2.421 (3)	Cu2—Cu1A^xiv	2.62 (2)
Cu1B—Cu1B^x	2.74 (3)	Cu1A—Se01^ix	2.419 (6)
Cu1B—Cu2^xi	2.791 (9)	Cu1A—Se01^viii	2.419 (6)
Cu1B—Cu2^xii	2.654 (15)	Cu1A—Se01^xvii	2.56 (3)
Cu1B—Cu2^viii	2.654 (15)	Cu1A—Cu2^xv	2.62 (2)
Cu1B—Cu2^xiii	2.045 (13)	Cu1A—Cu2^xiii	2.62 (2)
Cu1B—Cu2^xiv	2.045 (13)	Cu1A—Cu2^xiv	2.62 (2)

Cu1Bⁱ—Se01—Cu1Bⁱⁱ	115.8 (2)	Cu2^xiv—Cu1B—Cu2^viii	110.0 (7)
Cu1Bⁱ—Se01—Cu1B	115.8 (2)	Cu2^xiv—Cu1B—Cu2^x	115.1 (5)
Cu1Bⁱⁱ—Se01—Cu1B	115.8 (2)	Cu2^xv—Cu1B—Cu2^xii	52.0 (3)
Cu1Bⁱⁱ—Se01—Cu2^vi	68.3 (3)	Cu2^xiii—Cu1B—Cu2^x	100.2 (4)
Cu1B—Se01—Cu2	84.1 (4)	Cu2^vii—Cu1B—Cu2^x	116.2 (5)
Cu1Bⁱ—Se01—Cu2^iv	48.5 (3)	Cu2^xiii—Cu1B—Cu2^xi	115.1 (5)
Cu1Bⁱⁱ—Se01—Cu2^v	48.5 (3)	Cu2^xiii—Cu1B—Cu2^xii	110.0 (7)
Cu1Bⁱ—Se01—Cu2^vi	48.5 (3)	Cu2^xv—Cu1B—Cu2^xiii	103.9 (5)
Cu1Bⁱ—Se01—Cu2	84.1 (4)	Cu2^xii—Cu1B—Cu2^vii	74.8 (5)
Cu1Bⁱⁱ—Se01—Cu2	66.0 (5)	Cu2^xiii—Cu1B—Cu2^vii	52.0 (3)
Cu1B—Se01—Cu2ⁱⁱⁱ	84.1 (4)	Cu2^xv—Cu1B—Cu2^viii	52.0 (3)
Cu1B—Se01—Cu2^v	134.5 (4)	Cu2^xii—Cu1B—Cu2^xi	50.1 (2)
Cu1Bⁱ—Se01—Cu2^vii	84.1 (4)	Cu2^x—Cu1B—Cu2^xi	18.1 (4)
Cu1Bⁱ—Se01—Cu2^v	68.3 (3)	Cu2^xiv—Cu1B—Cu2^vii	52.0 (3)
Cu1Bⁱⁱ—Se01—Cu2^vii	84.1 (4)	Cu2^xii—Cu1B—Cu2^x	63.2 (3)
Cu1Bⁱ—Se01—Cu2ⁱⁱⁱ	66.0 (5)	Cu2^xiii—Cu1B—Cu2^xiv	103.9 (5)
Cu1B—Se01—Cu2^iv	68.3 (3)	Cu2^viii—Cu1B—Cu2^xii	74.8 (5)
Cu1Bⁱⁱ—Se01—Cu2^iv	134.5 (4)	Cu2^xiii—Cu1B—Cu2^viii	52.0 (3)
Cu1B—Se01—Cu2^vi	134.5 (4)	Cu2^xiv—Cu1B—Cu2^xi	100.2 (4)
Cu1Bⁱⁱ—Se01—Cu2ⁱⁱⁱ	84.1 (4)	Se01^vi—Cu2—Se01^xiv	107.2 (4)
Cu1B—Se01—Cu2^vii	66.0 (4)	Se01—Cu2—Se01^xiv	125.07 (19)
Cu2^vii—Se01—Cu2	20.7 (5)	Se01—Cu2—Se01^vi	125.08 (19)
Cu2ⁱⁱⁱ—Se01—Cu2^iv	50.5 (3)	Se01^vi—Cu2—Cu1Bⁱⁱ	101.1 (3)
Cu2^v—Se01—Cu2^iv	94.4 (3)	Se01—Cu2—Cu1Bⁱⁱ	56.5 (3)
Cu2^vii—Se01—Cu2^vi	69.7 (3)	Se01^xiv—Cu2—Cu1Bⁱⁱ	101.1 (3)
Cu2^vi—Se01—Cu2^v	19.9 (5)	Se01—Cu2—Cu1A^xiv	146.8 (7)
Cu2^vi—Se01—Cu2^iv	78.4 (5)	Se01^xiv—Cu2—Cu1A^xiv	55.8 (2)
Cu2ⁱⁱⁱ—Se01—Cu2^v	54.93 (19)	Se01^vi—Cu2—Cu1A^xiv	55.8 (2)
Cu2ⁱⁱⁱ—Se01—Cu2^vii	20.7 (5)	Cu1B^xiv—Cu2—Se01	126.5 (6)
Cu2—Se01—Cu2^iv	69.7 (3)	Cu1B^xiv—Cu2—Se01^xiv	62.5 (3)
Cu2^vii—Se01—Cu2^iv	54.93 (19)	Cu1B^xiv—Cu2—Se01^vi	62.5 (3)
Cu2—Se01—Cu2^vi	54.93 (19)	Cu1B^xiv—Cu2—Cu1Bⁱⁱ	70.1 (7)
Cu2ⁱⁱⁱ—Se01—Cu2	20.7 (5)	Cu1B^xiv—Cu2—Cu2^v	78.8 (3)
Cu2^vii—Se01—Cu2^v	69.7 (3)	Cu1B^xiv—Cu2—Cu2^xvi	78.8 (3)
Cu2ⁱⁱⁱ—Se01—Cu2^vi	50.5 (3)	Cu1B^xiv—Cu2—Cu2^xiv	97.0 (7)
Cu2—Se01—Cu2^v	50.5 (3)	Cu1B^xiv—Cu2—Cu2^vi	97.0 (6)
Cu1Aⁱⁱ—Se01—Cu2^v	63.7 (6)	Cu2^xiv—Cu2—Se01^vi	159.4 (8)
Cu1Aⁱ—Se01—Cu2	107.5 (7)	Cu2^xiv—Cu2—Se01^xiv	60.4 (3)
Cu1A—Se01—Cu2^vii	89.8 (8)	Cu2^xvi—Cu2—Se01^xiv	62.4 (3)
Cu1Aⁱⁱ—Se01—Cu2	89.8 (8)	Cu2^vii—Cu2—Se01^vi	129.2 (3)
Cu1Aⁱ—Se01—Cu2^vi	63.7 (6)	Cu2^v—Cu2—Se01^xiv	138.8 (3)
Cu1A—Se01—Cu2^vi	157.0 (7)	Cu2^vi—Cu2—Se01	64.7 (4)
Cu1Aⁱⁱ—Se01—Cu2^iv	157.0 (7)	Cu2^xvi—Cu2—Se01	67.2 (4)
Cu1Aⁱ—Se01—Cu2^v	81.3 (5)	Cu2^v—Cu2—Se01	67.2 (4)
Cu1Aⁱⁱ—Se01—Cu2^vii	107.5 (7)	Cu2^v—Cu2—Se01^vi	62.4 (3)
Cu1Aⁱⁱ—Se01—Cu2^vi	81.3 (5)	Cu2ⁱⁱⁱ—Cu2—Se01^xiv	129.2 (3)
Cu1Aⁱ—Se01—Cu2^vii	107.5 (7)	Cu2^xiv—Cu2—Se01	64.7 (4)
Cu1A—Se01—Cu2^v	157.0 (7)	Cu2^vi—Cu2—Se01^xiv	159.4 (8)
Cu1A—Se01—Cu2ⁱⁱⁱ	107.5 (7)	Cu2^xvi—Cu2—Se01^vi	138.8 (3)
Cu1Aⁱ—Se01—Cu2ⁱⁱⁱ	89.8 (8)	Cu2^vii—Cu2—Se01^xiv	80.1 (3)
Cu1Aⁱ—Se01—Cu2^iv	63.7 (6)	Cu2^vi—Cu2—Se01^vi	60.4 (3)
Cu1A—Se01—Cu2	107.5 (7)	Cu2ⁱⁱⁱ—Cu2—Se01	79.7 (2)
Cu1A—Se01—Cu2^iv	81.3 (5)	Cu2ⁱⁱⁱ—Cu2—Se01^vi	80.1 (3)
Cu1Aⁱⁱ—Se01—Cu2ⁱⁱⁱ	107.5 (7)	Cu2^vii—Cu2—Se01	79.7 (2)
Cu1Aⁱⁱ—Se01—Cu1A	115.9 (5)	Cu2ⁱⁱⁱ—Cu2—Cu1B^xiv	142.0 (3)
Cu1Aⁱⁱ—Se01—Cu1Aⁱ	115.9 (5)	Cu2^xvi—Cu2—Cu1Bⁱⁱ	49.1 (3)
Cu1Aⁱ—Se01—Cu1A	115.9 (5)	Cu2^vii—Cu2—Cu1Bⁱⁱ	127.4 (2)
Se01^viii—Cu1B—Se01	115.8 (2)	Cu2^v—Cu2—Cu1Bⁱⁱ	49.1 (3)
Se01^ix—Cu1B—Se01^viii	115.8 (2)	Cu2ⁱⁱⁱ—Cu2—Cu1Bⁱⁱ	127.4 (3)
Se01^ix—Cu1B—Se01	115.8 (2)	Cu2^xiv—Cu2—Cu1Bⁱⁱ	68.1 (5)
Se01—Cu1B—Cu1B^x	102.0 (4)	Cu2^vii—Cu2—Cu1B^xiv	142.0 (3)
Se01^viii—Cu1B—Cu1B^x	102.0 (4)	Cu2^vi—Cu2—Cu1Bⁱⁱ	68.1 (5)
Se01^ix—Cu1B—Cu1B^x	102.0 (4)	Cu2^v—Cu2—Cu2^xiv	114.8 (7)
Se01—Cu1B—Cu2^x	169.2 (4)	Cu2ⁱⁱⁱ—Cu2—Cu2^xvi	139.1 (3)
Se01^viii—Cu1B—Cu2^x	58.0 (2)	Cu2^vii—Cu2—Cu2^v	139.1 (3)
Se01—Cu1B—Cu2^vii	57.5 (3)	Cu2ⁱⁱⁱ—Cu2—Cu2^vii	60.001 (5)
Se01^viii—Cu1B—Cu2^xi	74.78 (18)	Cu2^vi—Cu2—Cu2^xiv	125.5 (8)
Se01^ix—Cu1B—Cu2^xi	58.0 (2)	Cu2^xvi—Cu2—Cu2^vi	114.8 (7)
Se01^ix—Cu1B—Cu2^x	74.78 (18)	Cu2^vii—Cu2—Cu2^vi	120.5 (6)
Se01^viii—Cu1B—Cu2^xii	119.4 (3)	Cu2^v—Cu2—Cu2^xvi	98.1 (6)
Se01—Cu1B—Cu2^xi	169.2 (4)	Cu2^vii—Cu2—Cu2^xvi	89.999 (8)
Se01^ix—Cu1B—Cu2^vii	119.4 (3)	Cu2ⁱⁱⁱ—Cu2—Cu2^v	90.000 (9)
Se01^ix—Cu1B—Cu2^viii	119.4 (3)	Cu2ⁱⁱⁱ—Cu2—Cu2^xiv	120.5 (6)
Se01^viii—Cu1B—Cu2^vii	119.4 (3)	Cu2ⁱⁱⁱ—Cu2—Cu2^vi	67.6 (6)
Se01^viii—Cu1B—Cu2^viii	57.5 (3)	Cu2^vii—Cu2—Cu2^xiv	67.6 (6)
Se01—Cu1B—Cu2^xii	119.4 (3)	Cu2^v—Cu2—Cu2^vi	22.4 (6)
Se01^ix—Cu1B—Cu2^xii	57.5 (3)	Cu2^xvi—Cu2—Cu2^xiv	22.4 (6)
Se01—Cu1B—Cu2^viii	119.4 (3)	Cu2^vii—Cu2—Cu1A^xiv	127.9 (4)
Cu1B^x—Cu1B—Cu2^xi	72.3 (3)	Cu2^xvi—Cu2—Cu1A^xiv	92.0 (4)
Cu1B^x—Cu1B—Cu2^x	72.3 (3)	Cu2^v—Cu2—Cu1A^xiv	92.0 (4)
Cu2^xv—Cu1B—Se01	167.5 (8)	Cu2ⁱⁱⁱ—Cu2—Cu1A^xiv	127.9 (4)
Cu2^xiii—Cu1B—Se01^viii	69.00 (12)	Cu2^vi—Cu2—Cu1A^xiv	105.5 (6)
Cu2^xiv—Cu1B—Se01^viii	167.5 (8)	Cu2^xiv—Cu2—Cu1A^xiv	105.5 (6)
Cu2^xiv—Cu1B—Se01^ix	69.00 (12)	Se01^viii—Cu1A—Se01	115.9 (5)
Cu2^xv—Cu1B—Se01^viii	69.00 (12)	Se01^viii—Cu1A—Se01^ix	115.9 (5)
Cu2^xiii—Cu1B—Se01	69.00 (12)	Se01^ix—Cu1A—Se01	115.9 (5)
Cu2^xv—Cu1B—Se01^ix	69.00 (12)	Se01^viii—Cu1A—Se01^xvii	101.8 (7)
Cu2^xiv—Cu1B—Se01	69.00 (12)	Se01^ix—Cu1A—Se01^xvii	101.8 (7)
Cu2^xiii—Cu1B—Se01^ix	167.5 (8)	Se01—Cu1A—Se01^xvii	101.8 (7)
Cu2^xv—Cu1B—Cu1B^x	65.4 (5)	Se01^viii—Cu1A—Cu2^xiii	60.6 (4)
Cu2^vii—Cu1B—Cu1B^x	44.5 (3)	Se01^xvii—Cu1A—Cu2^xv	134.8 (5)
Cu2^xiv—Cu1B—Cu1B^x	65.4 (5)	Se01—Cu1A—Cu2^xv	123.4 (12)
Cu2^xii—Cu1B—Cu1B^x	44.5 (3)	Se01^ix—Cu1A—Cu2^xiii	123.4 (12)
Cu2^viii—Cu1B—Cu1B^x	44.5 (3)	Se01^viii—Cu1A—Cu2^xiv	123.4 (12)
Cu2^xiii—Cu1B—Cu1B^x	65.4 (5)	Se01^ix—Cu1A—Cu2^xv	60.6 (4)
Cu2^viii—Cu1B—Cu2^vii	74.8 (5)	Se01^xvii—Cu1A—Cu2^xiv	134.8 (5)
Cu2^viii—Cu1B—Cu2^xi	63.2 (3)	Se01—Cu1A—Cu2^xiv	60.6 (4)
Cu2^xiv—Cu1B—Cu2^xii	52.0 (3)	Se01^viii—Cu1A—Cu2^xv	60.6 (4)
Cu2^xv—Cu1B—Cu2^xi	11.2 (3)	Se01^ix—Cu1A—Cu2^xiv	60.6 (4)
Cu2^xv—Cu1B—Cu2^x	11.2 (3)	Se01^xvii—Cu1A—Cu2^xiii	134.8 (5)
Cu2^viii—Cu1B—Cu2^x	50.1 (2)	Se01—Cu1A—Cu2^xiii	60.6 (4)
Cu2^xv—Cu1B—Cu2^vii	110.0 (7)	Cu2^xv—Cu1A—Cu2^xiii	75.8 (8)
Cu2^xv—Cu1B—Cu2^xiv	103.9 (5)	Cu2^xv—Cu1A—Cu2^xiv	75.8 (8)
Cu2^vii—Cu1B—Cu2^xi	116.2 (5)	Cu2^xiii—Cu1A—Cu2^xiv	75.8 (8)

Symmetry codes: (i) x−1, y, z; (ii) x, y+1, z; (iii) −y+1, x−y+1, z; (iv) x−y+1/3, x−1/3, −z+2/3; (v) y−2/3, −x+y+2/3, −z+2/3; (vi) −x+1/3, −y+5/3, −z+2/3; (vii) −x+y, −x+1, z; (viii) x, y−1, z; (ix) x+1, y, z; (x) −x+4/3, −y+2/3, −z+2/3; (xi) y+1/3, −x+y−1/3, −z+2/3; (xii) −y+2, x−y+1, z; (xiii) y−2/3, −x+y−1/3, −z+2/3; (xiv) −x+4/3, −y+5/3, −z+2/3; (xv) x−y+4/3, x−1/3, −z+2/3; (xvi) x−y+4/3, x+2/3, −z+2/3; (xvii) −x+1, −y+1, −z+1.

(Cu2-xSe_bulk_100K) top

Crystal data top

0.33(Cu_5.66Se₃)	D_x = 6.625 Mg m⁻³
M_r = 198.94	Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3m	Cell parameters from 154 reflections
a = 4.1019 (16) Å	θ = 3.0–24.2°
c = 20.533 (9) Å	µ = 37.88 mm⁻¹
V = 299.2 (3) Å³	T = 100 K
Z = 6	Plate, metallic grayish gray
F(000) = 533	0.07 × 0.03 × 0.02 mm

Data collection top

SuperNova, Single source at offset, Atlas diffractometer	72 independent reflections
Radiation source: micro-focus sealed X-ray tube, SuperNova (Mo) X-ray Source	63 reflections with I > 2σ(I)
Mirror monochromator	R_int = 0.141
Detector resolution: 10.3590 pixels mm^-1	θ_max = 23.2°, θ_min = 3.0°
ω scans	h = −4→4
Absorption correction: multi-scan CrysAlisPro 1.171.38.41 (Rigaku Oxford Diffraction, 2015) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	k = −4→4
T_min = 0.316, T_max = 1.000	l = −22→22
785 measured reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Primary atom site location: structure-invariant direct methods
R[F² > 2σ(F²)] = 0.079	w = 1/[σ²(F_o²) + (0.1541P)²] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.192	(Δ/σ)_max < 0.001
S = 1.07	Δρ_max = 2.74 e Å⁻³
72 reflections	Δρ_min = −1.28 e Å⁻³
15 parameters

Special details top

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Se	0.6667	0.3333	0.59295 (19)	0.045 (2)
Cu1B	0.6667	0.3333	0.7663 (4)	0.045 (2)	0.624 (14)
Cu1A	0.6667	0.3333	0.7171 (8)	0.045 (2)	0.329 (10)
Cu2	0.4035 (11)	0.5965 (11)	0.8091 (4)	0.049 (5)	0.312 (10)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Se	0.053 (2)	0.053 (2)	0.029 (3)	0.0267 (12)	0.000	0.000
Cu1B	0.053 (2)	0.053 (2)	0.029 (3)	0.0267 (12)	0.000	0.000
Cu1A	0.053 (2)	0.053 (2)	0.029 (3)	0.0267 (12)	0.000	0.000
Cu2	0.064 (6)	0.064 (6)	0.026 (5)	0.039 (4)	−0.0005 (16)	0.0005 (16)

Geometric parameters (Å, º) top

Se—Cu1Bⁱ	2.427 (2)	Cu1B—Cu2^xi	2.066 (9)
Se—Cu1Bⁱⁱ	2.427 (2)	Cu1B—Cu2^xii	2.646 (10)
Se—Cu1Bⁱⁱⁱ	2.427 (2)	Cu1B—Cu2^xiii	2.646 (10)
Se—Cu1Aⁱ	2.416 (4)	Cu1B—Cu2^xiv	2.066 (9)
Se—Cu1Aⁱⁱⁱ	2.416 (4)	Cu1A—Seⁱ	2.416 (4)
Se—Cu1A	2.550 (15)	Cu1A—Seⁱⁱⁱ	2.416 (4)
Se—Cu1Aⁱⁱ	2.416 (4)	Cu1A—Seⁱⁱ	2.416 (4)
Se—Cu2^iv	2.457 (8)	Cu1A—Cu2^xiv	2.658 (14)
Se—Cu2^v	2.457 (8)	Cu1A—Cu2^xi	2.658 (14)
Se—Cu2^vi	2.457 (8)	Cu1A—Cu2	2.658 (14)
Se—Cu2^vii	2.582 (5)	Cu2—Seⁱⁱⁱ	2.582 (5)
Se—Cu2^viii	2.582 (5)	Cu2—Seⁱⁱ	2.582 (5)
Cu1B—Seⁱ	2.427 (2)	Cu2—Se^xv	2.457 (8)
Cu1B—Seⁱⁱⁱ	2.427 (2)	Cu2—Cu1B^ix	2.646 (10)
Cu1B—Seⁱⁱ	2.427 (2)	Cu2—Cu2^xvi	0.864 (14)
Cu1B—Cu1B^ix	2.751 (15)	Cu2—Cu2^xiii	2.117 (10)
Cu1B—Cu1A	1.010 (15)	Cu2—Cu2^xvii	2.287 (7)
Cu1B—Cu2^x	2.795 (6)	Cu2—Cu2^xii	2.117 (10)
Cu1B—Cu2	2.066 (8)	Cu2—Cu2^xviii	0.864 (14)
Cu1B—Cu2^ix	2.646 (10)	Cu2—Cu2^xix	2.287 (7)

Cu1Bⁱ—Se—Cu1Bⁱⁱ	115.32 (14)	Cu2^xi—Cu1B—Cu2^x	11.07 (18)
Cu1Bⁱ—Se—Cu1Bⁱⁱⁱ	115.32 (14)	Cu2—Cu1B—Cu2^x	114.3 (3)
Cu1Bⁱⁱ—Se—Cu1Bⁱⁱⁱ	115.32 (14)	Cu2^xi—Cu1B—Cu2^xiii	51.63 (17)
Cu1Bⁱⁱ—Se—Cu1A	102.7 (2)	Cu2—Cu1B—Cu2^xii	51.63 (17)
Cu1Bⁱⁱⁱ—Se—Cu1A	102.68 (19)	Cu2^xiv—Cu1B—Cu2^x	99.7 (3)
Cu1Bⁱ—Se—Cu1A	102.7 (2)	Cu2—Cu1B—Cu2^ix	109.8 (4)
Cu1Bⁱ—Se—Cu2^iv	83.3 (2)	Cu2^xi—Cu1B—Cu2^xiv	103.2 (3)
Cu1Bⁱⁱⁱ—Se—Cu2^v	83.3 (2)	Cu2^xiv—Cu1B—Cu2	103.2 (3)
Cu1Bⁱ—Se—Cu2^vii	48.58 (18)	Cu2^xi—Cu1B—Cu2^xii	109.8 (4)
Cu1Bⁱⁱⁱ—Se—Cu2^iv	83.3 (2)	Cu2^xi—Cu1B—Cu2	103.2 (3)
Cu1Bⁱ—Se—Cu2^viii	48.58 (18)	Cu2^xii—Cu1B—Cu2^x	116.1 (3)
Cu1Bⁱⁱⁱ—Se—Cu2^viii	67.7 (2)	Cu2^xiv—Cu1B—Cu2^ix	51.63 (17)
Cu1Bⁱⁱ—Se—Cu2^v	83.3 (2)	Cu2^xiii—Cu1B—Cu2^ix	75.4 (3)
Cu1Bⁱ—Se—Cu2^v	65.6 (3)	Cu2^xiii—Cu1B—Cu2^xii	75.4 (3)
Cu1Bⁱⁱⁱ—Se—Cu2^vi	65.6 (3)	Cu2^ix—Cu1B—Cu2^x	49.62 (15)
Cu1Bⁱⁱⁱ—Se—Cu2^vii	132.9 (3)	Cu2^xii—Cu1B—Cu2^ix	75.4 (3)
Cu1Bⁱⁱ—Se—Cu2^iv	65.6 (3)	Cu2^xiii—Cu1B—Cu2^x	62.69 (18)
Cu1Bⁱⁱ—Se—Cu2^vi	83.3 (2)	Cu2^xiv—Cu1B—Cu2^xii	51.63 (17)
Cu1Bⁱ—Se—Cu2^vi	83.3 (2)	Cu2^xi—Cu1B—Cu2^ix	51.63 (17)
Cu1Bⁱⁱ—Se—Cu2^vii	67.7 (2)	Seⁱ—Cu1A—Seⁱⁱ	116.2 (3)
Cu1Bⁱⁱ—Se—Cu2^viii	132.9 (3)	Seⁱⁱⁱ—Cu1A—Se	101.4 (4)
Cu1Aⁱ—Se—Cu1Bⁱⁱ	121.44 (5)	Seⁱ—Cu1A—Seⁱⁱⁱ	116.2 (3)
Cu1Aⁱⁱ—Se—Cu1Bⁱⁱ	24.1 (4)	Seⁱ—Cu1A—Se	101.4 (4)
Cu1Aⁱⁱⁱ—Se—Cu1Bⁱⁱ	121.44 (5)	Seⁱⁱⁱ—Cu1A—Seⁱⁱ	116.2 (3)
Cu1Aⁱⁱ—Se—Cu1Bⁱⁱⁱ	121.44 (5)	Seⁱⁱ—Cu1A—Se	101.4 (4)
Cu1Aⁱ—Se—Cu1Bⁱ	24.1 (4)	Seⁱ—Cu1A—Cu2	123.3 (7)
Cu1Aⁱ—Se—Cu1Bⁱⁱⁱ	121.44 (5)	Seⁱⁱⁱ—Cu1A—Cu2	61.0 (2)
Cu1Aⁱⁱⁱ—Se—Cu1Bⁱ	121.44 (5)	Se—Cu1A—Cu2^xi	135.3 (3)
Cu1Aⁱⁱ—Se—Cu1Bⁱ	121.44 (5)	Seⁱⁱⁱ—Cu1A—Cu2^xiv	123.3 (7)
Cu1Aⁱⁱⁱ—Se—Cu1Bⁱⁱⁱ	24.1 (4)	Se—Cu1A—Cu2	135.3 (3)
Cu1Aⁱ—Se—Cu1Aⁱⁱⁱ	116.2 (3)	Seⁱ—Cu1A—Cu2^xi	61.0 (2)
Cu1Aⁱⁱ—Se—Cu1A	78.6 (4)	Seⁱ—Cu1A—Cu2^xiv	61.0 (2)
Cu1Aⁱ—Se—Cu1A	78.6 (4)	Seⁱⁱ—Cu1A—Cu2^xi	123.3 (7)
Cu1Aⁱ—Se—Cu1Aⁱⁱ	116.2 (3)	Seⁱⁱ—Cu1A—Cu2^xiv	61.0 (2)
Cu1Aⁱⁱⁱ—Se—Cu1Aⁱⁱ	116.2 (3)	Se—Cu1A—Cu2^xiv	135.3 (3)
Cu1Aⁱⁱⁱ—Se—Cu1A	78.6 (4)	Seⁱⁱ—Cu1A—Cu2	61.0 (2)
Cu1A—Se—Cu2^viii	123.13 (17)	Seⁱⁱⁱ—Cu1A—Cu2^xi	61.0 (2)
Cu1Aⁱⁱⁱ—Se—Cu2^vi	89.7 (5)	Cu1B—Cu1A—Seⁱⁱⁱ	78.6 (4)
Cu1Aⁱ—Se—Cu2^vii	64.1 (3)	Cu1B—Cu1A—Seⁱⁱ	78.6 (4)
Cu1Aⁱ—Se—Cu2^viii	64.1 (3)	Cu1B—Cu1A—Seⁱ	78.6 (4)
Cu1Aⁱⁱ—Se—Cu2^vii	81.3 (3)	Cu1B—Cu1A—Se	180.0
Cu1Aⁱ—Se—Cu2^vi	107.0 (4)	Cu1B—Cu1A—Cu2^xiv	44.7 (3)
Cu1Aⁱⁱ—Se—Cu2^v	107.0 (4)	Cu1B—Cu1A—Cu2^xi	44.7 (3)
Cu1Aⁱⁱⁱ—Se—Cu2^v	107.0 (4)	Cu1B—Cu1A—Cu2	44.7 (3)
Cu1Aⁱⁱⁱ—Se—Cu2^viii	81.3 (3)	Cu2^xiv—Cu1A—Cu2	75.1 (5)
Cu1Aⁱⁱ—Se—Cu2^iv	89.7 (5)	Cu2^xi—Cu1A—Cu2	75.1 (5)
Cu1Aⁱⁱ—Se—Cu2^viii	155.8 (5)	Cu2^xi—Cu1A—Cu2^xiv	75.1 (5)
Cu1Aⁱ—Se—Cu2^iv	107.0 (4)	Se^xv—Cu2—Seⁱⁱ	126.09 (17)
Cu1Aⁱ—Se—Cu2^v	89.7 (5)	Se^xv—Cu2—Seⁱⁱⁱ	126.09 (17)
Cu1Aⁱⁱⁱ—Se—Cu2^vii	155.8 (5)	Seⁱⁱ—Cu2—Seⁱⁱⁱ	105.2 (3)
Cu1Aⁱⁱ—Se—Cu2^vi	107.0 (4)	Se^xv—Cu2—Cu1B^ix	56.7 (2)
Cu1Aⁱⁱⁱ—Se—Cu2^iv	107.0 (4)	Seⁱⁱⁱ—Cu2—Cu1B^ix	101.5 (2)
Cu1A—Se—Cu2^vii	123.13 (17)	Seⁱⁱ—Cu2—Cu1B^ix	101.5 (2)
Cu2^v—Se—Cu1A	168.29 (19)	Seⁱⁱⁱ—Cu2—Cu1A	54.89 (16)
Cu2^vi—Se—Cu1A	168.3 (2)	Se^xv—Cu2—Cu1A	147.0 (4)
Cu2^iv—Se—Cu1A	168.3 (2)	Seⁱⁱ—Cu2—Cu1A	54.89 (16)
Cu2^iv—Se—Cu2^viii	68.4 (2)	Cu1B—Cu2—Se^xv	126.9 (4)
Cu2^v—Se—Cu2^viii	49.6 (2)	Cu1B—Cu2—Seⁱⁱⁱ	61.79 (18)
Cu2^v—Se—Cu2^vii	49.6 (2)	Cu1B—Cu2—Seⁱⁱ	61.79 (18)
Cu2^iv—Se—Cu2^vi	20.2 (3)	Cu1B—Cu2—Cu1B^ix	70.2 (4)
Cu2^vi—Se—Cu2^vii	68.4 (2)	Cu1B^ix—Cu2—Cu1A	90.3 (4)
Cu2^v—Se—Cu2^vi	20.2 (3)	Cu1B—Cu2—Cu1A	20.1 (3)
Cu2^v—Se—Cu2^iv	20.2 (3)	Cu1B—Cu2—Cu2^xiii	78.5 (2)
Cu2^vi—Se—Cu2^viii	53.91 (17)	Cu1B—Cu2—Cu2^xix	96.4 (4)
Cu2^vii—Se—Cu2^viii	77.7 (4)	Cu1B—Cu2—Cu2^xvii	96.4 (4)
Cu2^iv—Se—Cu2^vii	53.91 (17)	Cu1B—Cu2—Cu2^xii	78.5 (2)
Seⁱ—Cu1B—Seⁱⁱⁱ	115.32 (14)	Cu2^xvi—Cu2—Se^xv	79.88 (16)
Seⁱ—Cu1B—Seⁱⁱ	115.32 (14)	Cu2^xviii—Cu2—Seⁱⁱⁱ	80.37 (19)
Seⁱⁱ—Cu1B—Seⁱⁱⁱ	115.32 (14)	Cu2^xiii—Cu2—Seⁱⁱⁱ	62.1 (3)
Seⁱⁱⁱ—Cu1B—Cu1B^ix	102.7 (2)	Cu2^xvii—Cu2—Seⁱⁱⁱ	158.2 (6)
Seⁱⁱ—Cu1B—Cu1B^ix	102.68 (19)	Cu2^xvii—Cu2—Se^xv	65.8 (3)
Seⁱ—Cu1B—Cu1B^ix	102.7 (2)	Cu2^xvi—Cu2—Seⁱⁱ	80.37 (19)
Seⁱⁱⁱ—Cu1B—Cu2^xiii	57.73 (19)	Cu2^xii—Cu2—Se^xv	68.3 (4)
Seⁱⁱ—Cu1B—Cu2^x	169.4 (2)	Cu2^xix—Cu2—Seⁱⁱⁱ	60.2 (2)
Seⁱ—Cu1B—Cu2^xiii	120.00 (17)	Cu2^xix—Cu2—Seⁱⁱ	158.2 (6)
Seⁱ—Cu1B—Cu2^xii	120.00 (17)	Cu2^xvii—Cu2—Seⁱⁱ	60.2 (2)
Seⁱⁱ—Cu1B—Cu2^xii	57.73 (19)	Cu2^xiii—Cu2—Se^xv	68.3 (4)
Seⁱⁱⁱ—Cu1B—Cu2^x	75.09 (13)	Cu2^xvi—Cu2—Seⁱⁱⁱ	128.83 (17)
Seⁱⁱⁱ—Cu1B—Cu2^ix	120.00 (17)	Cu2^xiii—Cu2—Seⁱⁱ	138.3 (2)
Seⁱⁱⁱ—Cu1B—Cu2^xii	120.00 (17)	Cu2^xviii—Cu2—Seⁱⁱ	128.83 (17)
Seⁱ—Cu1B—Cu2^ix	57.73 (18)	Cu2^xii—Cu2—Seⁱⁱ	62.1 (3)
Seⁱⁱ—Cu1B—Cu2^ix	120.00 (17)	Cu2^xviii—Cu2—Se^xv	79.88 (16)
Seⁱⁱ—Cu1B—Cu2^xiii	120.00 (17)	Cu2^xix—Cu2—Se^xv	65.8 (3)
Seⁱ—Cu1B—Cu2^x	58.77 (16)	Cu2^xii—Cu2—Seⁱⁱⁱ	138.3 (2)
Cu1B^ix—Cu1B—Cu2^x	71.7 (2)	Cu2^xvi—Cu2—Cu1B	141.61 (17)
Cu1A—Cu1B—Seⁱ	77.3 (2)	Cu2^xiii—Cu2—Cu1B^ix	49.9 (2)
Cu1A—Cu1B—Seⁱⁱ	77.32 (19)	Cu2^xviii—Cu2—Cu1B^ix	127.72 (17)
Cu1A—Cu1B—Seⁱⁱⁱ	77.3 (2)	Cu2^xix—Cu2—Cu1B^ix	68.6 (4)
Cu1A—Cu1B—Cu1B^ix	180.0	Cu2^xvi—Cu2—Cu1B^ix	127.72 (17)
Cu1A—Cu1B—Cu2^xiv	115.2 (3)	Cu2^xvii—Cu2—Cu1B^ix	68.6 (4)
Cu1A—Cu1B—Cu2	115.2 (3)	Cu2^xii—Cu2—Cu1B^ix	49.9 (2)
Cu1A—Cu1B—Cu2^xiii	135.0 (2)	Cu2^xviii—Cu2—Cu1B	141.61 (17)
Cu1A—Cu1B—Cu2^x	108.3 (2)	Cu2^xviii—Cu2—Cu1A	127.5 (2)
Cu1A—Cu1B—Cu2^ix	135.0 (2)	Cu2^xix—Cu2—Cu1A	104.6 (4)
Cu1A—Cu1B—Cu2^xi	115.2 (3)	Cu2^xvii—Cu2—Cu1A	104.6 (4)
Cu1A—Cu1B—Cu2^xii	135.0 (2)	Cu2^xii—Cu2—Cu1A	91.3 (3)
Cu2^xi—Cu1B—Seⁱⁱⁱ	69.63 (11)	Cu2^xiii—Cu2—Cu1A	91.3 (3)
Cu2^xiv—Cu1B—Seⁱ	69.63 (11)	Cu2^xvi—Cu2—Cu1A	127.5 (2)
Cu2—Cu1B—Seⁱ	167.5 (4)	Cu2^xiii—Cu2—Cu2^xix	22.2 (4)
Cu2^xiv—Cu1B—Seⁱⁱⁱ	167.5 (4)	Cu2^xvi—Cu2—Cu2^xii	90.000 (13)
Cu2—Cu1B—Seⁱⁱⁱ	69.63 (11)	Cu2^xii—Cu2—Cu2^xix	116.5 (6)
Cu2^xi—Cu1B—Seⁱⁱ	167.5 (4)	Cu2^xiii—Cu2—Cu2^xii	99.7 (5)
Cu2—Cu1B—Seⁱⁱ	69.63 (11)	Cu2^xvi—Cu2—Cu2^xvii	67.8 (4)
Cu2^xiv—Cu1B—Seⁱⁱ	69.63 (11)	Cu2^xviii—Cu2—Cu2^xii	139.9 (2)
Cu2^xi—Cu1B—Seⁱ	69.63 (11)	Cu2^xii—Cu2—Cu2^xvii	22.2 (4)
Cu2—Cu1B—Cu1B^ix	64.8 (3)	Cu2^xiii—Cu2—Cu2^xvii	116.5 (6)
Cu2^xii—Cu1B—Cu1B^ix	45.0 (2)	Cu2^xvi—Cu2—Cu2^xix	121.3 (4)
Cu2^ix—Cu1B—Cu1B^ix	45.0 (2)	Cu2^xviii—Cu2—Cu2^xiii	90.000 (16)
Cu2^xiii—Cu1B—Cu1B^ix	45.0 (2)	Cu2^xviii—Cu2—Cu2^xvii	121.3 (4)
Cu2^xiv—Cu1B—Cu1B^ix	64.8 (3)	Cu2^xvi—Cu2—Cu2^xiii	139.9 (2)
Cu2^xi—Cu1B—Cu1B^ix	64.8 (3)	Cu2^xviii—Cu2—Cu2^xix	67.8 (4)
Cu2—Cu1B—Cu2^xiii	51.63 (17)	Cu2^xvi—Cu2—Cu2^xviii	60.00 (3)
Cu2^xiv—Cu1B—Cu2^xiii	109.8 (4)	Cu2^xix—Cu2—Cu2^xvii	127.5 (7)

Symmetry codes: (i) −x+5/3, −y+1/3, −z+4/3; (ii) −x+2/3, −y+1/3, −z+4/3; (iii) −x+5/3, −y+4/3, −z+4/3; (iv) −x+y+1/3, −x+2/3, z−1/3; (v) x+1/3, y−1/3, z−1/3; (vi) −y+4/3, x−y+2/3, z−1/3; (vii) x−y+2/3, x−2/3, −z+4/3; (viii) y+2/3, −x+y+1/3, −z+4/3; (ix) −x+4/3, −y+2/3, −z+5/3; (x) x+1, y, z; (xi) −x+y+1, −x+1, z; (xii) x−y+1/3, x−1/3, −z+5/3; (xiii) y+1/3, −x+y+2/3, −z+5/3; (xiv) −y+1, x−y, z; (xv) x−1/3, y+1/3, z+1/3; (xvi) −x+y, −x+1, z; (xvii) −x+1/3, −y+2/3, −z+5/3; (xviii) −y+1, x−y+1, z; (xix) −x+4/3, −y+5/3, −z+5/3.

Acknowledgements

This work was supported by the Danish National Research Foundation (Center for Materials Crystallography, DNRF93), and the Danish Center for Synchrotron and Neutron Research (Danscatt). The authors would like to acknowledge Mohammad Aref Hasen Mamakhel for STEM-EDX measurements. ABB would like to thank SINO Danish Center for funding. KAB is thankful for funding from the Danish Council for Independent Research (DFF), Grant No. 4090-00071, and the DFF Sapere Aude program. We gratefully acknowledge the RIKEN Harima institute for beam time at BL44B2 at the SPring-8 synchrotron facility.

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Volume 4| Part 4| July 2017| Pages 476-485

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