The low-temperature form of calcium gold stannide, CaAuSn

The EuAuGe-type CaAuSn phase has been synthesized and single-crystal X-ray diffraction analysis reveals that it has an ortho­rhom­bic symmetry (space group Imm2), with a = 4.5261 (7) Å, b = 7.1356 (11) Å and c = 7.8147 (11) Å. The structure features puckered layers that are connected by homoatomic Au-Au and Sn-Sn inter­layer bonds. This structure is one of the two parent structures of its high-temperature polymorph (ca 873 K), which is an inter­growth structure of the EuAuGe- and SrMgSi-type structures in a 2:3 ratio.

S1. Introduction

During exploratory syntheses of quasicrystals and approximants in the Ca–Au–Tr system (Tr = Ga, In, Ge, Sn; Lin & Corbett, 2007, 2008a,b, 2010a,b), the 1:1:1 phases were sometimes the minor products in inter­esting e/a (electron count per atom) regions. These phases were generally well characterized by single-crystal X-ray diffraction. According to the literature, both CaAuGa (Cordier et al., 1993) and CaAuIn (Kußmann et al., 1998) show SrMgSi-type (or TiNiSi-type) structures (space group Pnma). In comparison, the same 1:1:1 ratio yielded polymorphs when group 13 elements (Ga, In) were replaced by group 14 elements (Ge, Sn). For example, two polymorphs of CaAuGe were reported, i.e. a threefold superstructure (space group Pnma) of the SrMgSi-type (Merlo et al., 1998; Kußmann et al., 1998) and a monoclinic derivative (space group C2/m) (Merlo et al., 1998), whereas CaAuSn exhibits a fivefold superstructure (space group Pnma) of the SrMgSi-type parent structure (Kußmann et al., 1998). The formation of all these superstructures is incurred by different ordering between Au and Sn. In this work, we report another CaAuSn phase, which belongs to the EuAuGe-type (space group Imm2) structure (Pöttgen, 1995) and can also be considered as a parent of the CaAuSn superstructure.

S2. Experimental

High-purity elements of Ca, Au and Sn (all from Alfa Aesar, >99.99%) were weighed in the desired stoichiometries in an Ar-filled glove-box, and the mixtures were sealed in Ta containers using an arc melter under Ar. The Ta containers were then enclosed in SiO₂ tubes, which were evacuated down to 10 ^-6 Torr (1 Torr = 133.322 Pa). The samples were heated from room temperature to 1123 K at a rate of 120 K h^-1, kept at 1073 K for 1 d, slowly cooled to 773 K at a rate of 2 K h^-1, annealed at this temperature for three weeks and finally quenched in water. High-yield (> 95%) phase products were obtained from various loadings of CaAu_1+xSn_1-x (x ≤ ±0.2) proportions. All products are fragile, inert to air at room temperature and with a metallic luster.

S3. Refinements

A single crystal attached to a glass fiber was mounted on a Bruker SMART APEX CCD area-detector diffractometer equipped with Mo Kα (λ = 0.71069 Å) radiation. An exposure time of 10 s per frame at room temperature was adopted. The reflection intensities were integrated using the SAINT-Plus program in the SMART software package (Bruker, 2013). Empirical absorption corrections were accomplished with the aid of the SADABS subprogram (Sheldrick, 1996). The noncentrosymmetric space group was determined by the |E² - 1| test in XPREP within SHELXTL (Sheldrick, 2008). The structure was solved with the aid of direct methods and subsequently refined on |F²| with a combination of least-squares refinement and difference Fourier maps.

The Au and Sn sites were directly identified by direct methods. After a few cycles of least-square refinements, two independent sites with distances to the Au and Sn sites of ~3.05–3.10 Å were yielded by the difference Fourier map, so Ca was assigned to both sites. Final least-square refinements, with anisotropic displacement parameters, a secondary extinction correction and a constraint of an inversion twin for the noncentric symmetry, yielded R₁ = 0.0276, wR₂ = 0.0720 and a goodness-of-fit of 1.171 for 23 parameters refined from 330 observed independent data.

S4. Results and discussion

The present CaAuSn structure features two puckered layers, in which Au and Sn alterate along the c axis. There are two sets of Au—Sn bond distances in the puckered layers, i.e. 2.628 (1) and 2.663 (3) Å, the two shortest inter­atomic separations in the structure. Viewed along the a axis, adjacent puckered layers are connected by homo-atomic Au—Au [3.090 (2) Å] and Sn—Sn [2.746 (5) Å] inter­layer bonds, as shown in Fig. 1(a), whereas the electropositive Ca atoms are located in the large eight-membered rings. From another viewpoint, the Au–Sn three-dimensional framework can be considered as inter­linked ladders (circled with a red line in Fig. 1a), which consist of the above-mentioned inter­layer bonds. This structure differs from the SrMgSi-type by the `coloring' with regard to the inter­layer bonds (or ladders). As shown in Fig. 1(b), the SrMgSi-type structure consists only of hetero-atomic inter­layer bonds.

It turns out that the EuAuGe- and SrMgSi-type structures, both ordered derivatives of the KHg₂-type (or CeCu₂-type) structure (Hoffmann & Pöttgen, 2001), represent the two basic structural motifs for all the above-mentioned superstructures and others, which are actually inter­growth structures consisting of various proportions of the building blocks of the EuAuGe- and SrMgSi-type structures. Using A and B to represent the ladders of the EuAuGe- and SrMgSi-type structures, respectively, CaAuGe (Merlo et al., 1998; Kußmann et al., 1998) can be considered as a 4A+2B inter­growth structure, as shown in Fig. 2(a). Similarly, the structure of CaAuSn (Kußmann et al., 1998) is a 4A+6B inter­growth structure (Fig. 2b), EuAuSn (Pöttgen et al., 1997) is a 6A+4B inter­growth (Fig. 2c) and YPdSi (Prots' et al., 1998) is a 2A+2B inter­growth structure (Fig. 2d). Apparently, similar phases with other A+B combinations could exist and are to be discovered.

Related literature

For related literature, see: Bruker (2013); Cordier et al. (1993); Hoffmann & Pöttgen (2001); Kußmann, Hoffmann & Pöttgen (1998); Lin & Corbett (2007, 2008a, 2008b, 2010a, 2010b); Merlo et al. (1998); Pöttgen (1995); Pöttgen et al. (1997); Sheldrick (1996, 2008).

Computing details

Data collection: SMART (Bruker, 2002); cell refinement: SAINT-Plus (Bruker, 2013); data reduction: SAINT-Plus (Bruker, 2013); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2000); software used to prepare material for publication: SHELXTL2013 (Sheldrick, 2008).

Figures

	Fig. 1. Views of the 2 × 2 unit cells of (a) the EuAuGe-type CaAuSn along the a axis and (b) the SrMgSi-type EuZnSn along the b axis. In both plots, the areas circled by red lines mark the major coloring differences with regard to interlayer bonds or ladders.
	Fig. 2. The crystal structures of (a) CaAuGe, (b) CaAuSn, (c) EuAuSn and (d) YPdSi. The symbols `A' and `B' are used to show the differences among these intergrowth structures.

Calcium gold stannide

Crystal data

CaAuSn	Dx = 9.362 Mg m^−3
Mr = 355.74	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Imm2	Cell parameters from 330 reflections
a = 4.5261 (7) Å	θ = 3.9–28.2°
b = 7.1356 (11) Å	µ = 69.58 mm^−1
c = 7.8147 (11) Å	T = 273 K
V = 252.39 (7) Å^3	Irregular, metallic
Z = 4	0.03 × 0.02 × 0.02 mm
F(000) = 596

Data collection

Bruker SMART APEXII CCD area-detector diffractometer	326 reflections with I > 2σ(I)
Radiation source: Mo Ka	Rint = 0.024
ω scans	θmax = 28.2°, θmin = 3.9°
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996)	h = −5→5
Tmin = 0.16, Tmax = 0.27	k = −4→9
769 measured reflections	l = −10→9
330 independent reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	w = 1/[σ^2(Fo^2) + (0.036P)^2 + 7.6305P] where P = (Fo^2 + 2Fc^2)/3
R[F^2 > 2σ(F^2)] = 0.028	(Δ/σ)max < 0.001
wR(F^2) = 0.072	Δρmax = 2.68 e Å^−3
S = 1.17	Δρmin = −1.85 e Å^−3
330 reflections	Extinction correction: SHELXL2013 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
23 parameters	Extinction coefficient: 0.0072 (10)
1 restraint	Absolute structure: Refined as an inversion twin (Flack, 1983)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.31 (3)

Special details

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

Refinement. Refined as an inversion twin.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Au	0.0000	0.21650 (14)	0.68259 (7)	0.0106 (5)
Sn	0.0000	0.3076 (4)	0.0130 (3)	0.0163 (6)
Ca1	0.5000	0.5000	0.8058 (15)	0.0083 (18)
Ca2	0.0000	0.5000	0.3876 (16)	0.0109 (19)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Au	0.0111 (6)	0.0074 (6)	0.0133 (6)	0.000	0.000	0.0007 (7)
Sn	0.0145 (14)	0.0191 (10)	0.0153 (13)	0.000	0.000	0.0004 (9)
Ca1	0.010 (5)	0.006 (4)	0.009 (4)	0.000	0.000	0.000
Ca2	0.014 (6)	0.007 (4)	0.012 (5)	0.000	0.000	0.000

Geometric parameters (Å, º)

Au—Sn^i	2.6282 (13)	Ca1—Sn^xvi	3.103 (7)
Au—Sn^ii	2.6282 (13)	Ca1—Sn^iii	3.103 (7)
Au—Sn^iii	2.663 (3)	Ca1—Sn^xvii	3.103 (7)
Au—Ca2	3.067 (9)	Ca1—Sn^ii	3.171 (9)
Au—Au^iv	3.090 (2)	Ca1—Sn^xviii	3.171 (9)
Au—Ca2^v	3.174 (6)	Ca1—Au^xix	3.185 (4)
Au—Ca2^vi	3.174 (6)	Ca1—Au^xii	3.185 (4)
Au—Ca1^vii	3.185 (4)	Ca1—Au^xx	3.185 (4)
Au—Ca1	3.185 (4)	Ca1—Au^xviii	3.325 (11)
Au—Ca1^viii	3.325 (11)	Ca1—Au^ii	3.325 (11)
Sn—Au^ix	2.6282 (13)	Ca2—Au^xii	3.067 (9)
Sn—Au^x	2.6282 (13)	Ca2—Au^x	3.174 (6)
Sn—Au^xi	2.663 (3)	Ca2—Au^xxi	3.174 (6)
Sn—Sn^xii	2.746 (5)	Ca2—Au^xxii	3.174 (6)
Sn—Ca1^xiii	3.103 (7)	Ca2—Au^ix	3.174 (6)
Sn—Ca1^xi	3.103 (7)	Ca2—Sn^xii	3.233 (12)
Sn—Ca1^viii	3.171 (9)	Ca2—Sn^xviii	3.301 (4)
Sn—Ca2	3.233 (12)	Ca2—Sn^i	3.301 (4)
Sn—Ca2^viii	3.301 (4)	Ca2—Sn^ii	3.301 (4)
Sn—Ca2^xiv	3.301 (4)	Ca2—Sn^xxiii	3.301 (4)
Ca1—Sn^xv	3.103 (7)
Sn^i—Au—Sn^ii	118.87 (9)	Sn^xv—Ca1—Au^xix	50.09 (5)
Sn^i—Au—Sn^iii	120.33 (5)	Sn^xvi—Ca1—Au^xix	85.44 (6)
Sn^ii—Au—Sn^iii	120.33 (5)	Sn^iii—Ca1—Au^xix	163.2 (3)
Sn^i—Au—Ca2	70.38 (8)	Sn^xvii—Ca1—Au^xix	113.27 (9)
Sn^ii—Au—Ca2	70.38 (8)	Sn^ii—Ca1—Au^xix	102.8 (3)
Sn^iii—Au—Ca2	124.60 (17)	Sn^xviii—Ca1—Au^xix	48.85 (10)
Sn^i—Au—Au^iv	86.25 (6)	Au—Ca1—Au^xix	144.8 (4)
Sn^ii—Au—Au^iv	86.25 (6)	Sn^xv—Ca1—Au^xii	113.27 (9)
Sn^iii—Au—Au^iv	104.13 (6)	Sn^xvi—Ca1—Au^xii	163.2 (3)
Ca2—Au—Au^iv	131.27 (15)	Sn^iii—Ca1—Au^xii	85.44 (6)
Sn^i—Au—Ca2^v	146.78 (8)	Sn^xvii—Ca1—Au^xii	50.09 (5)
Sn^ii—Au—Ca2^v	66.97 (18)	Sn^ii—Ca1—Au^xii	102.8 (3)
Sn^iii—Au—Ca2^v	68.2 (2)	Sn^xviii—Ca1—Au^xii	48.85 (10)
Ca2—Au—Ca2^v	134.46 (14)	Au—Ca1—Au^xii	78.87 (11)
Au^iv—Au—Ca2^v	60.88 (7)	Au^xix—Ca1—Au^xii	90.57 (13)
Sn^i—Au—Ca2^vi	66.97 (18)	Sn^xv—Ca1—Au^xx	85.44 (6)
Sn^ii—Au—Ca2^vi	146.78 (8)	Sn^xvi—Ca1—Au^xx	50.09 (5)
Sn^iii—Au—Ca2^vi	68.2 (2)	Sn^iii—Ca1—Au^xx	113.27 (9)
Ca2—Au—Ca2^vi	134.46 (14)	Sn^xvii—Ca1—Au^xx	163.2 (3)
Au^iv—Au—Ca2^vi	60.88 (7)	Sn^ii—Ca1—Au^xx	48.85 (10)
Ca2^v—Au—Ca2^vi	91.0 (2)	Sn^xviii—Ca1—Au^xx	102.8 (3)
Sn^i—Au—Ca1^vii	65.30 (16)	Au—Ca1—Au^xx	90.57 (13)
Sn^ii—Au—Ca1^vii	143.71 (12)	Au^xix—Ca1—Au^xx	78.87 (11)
Sn^iii—Au—Ca1^vii	63.4 (2)	Au^xii—Ca1—Au^xx	144.8 (4)
Ca2—Au—Ca1^vii	78.95 (14)	Sn^xv—Ca1—Au^xviii	48.12 (15)
Au^iv—Au—Ca1^vii	129.44 (6)	Sn^xvi—Ca1—Au^xviii	75.1 (2)
Ca2^v—Au—Ca1^vii	131.5 (4)	Sn^iii—Ca1—Au^xviii	75.1 (2)
Ca2^vi—Au—Ca1^vii	69.50 (12)	Sn^xvii—Ca1—Au^xviii	48.12 (15)
Sn^i—Au—Ca1	143.71 (12)	Sn^ii—Ca1—Au^xviii	163.9 (3)
Sn^ii—Au—Ca1	65.30 (16)	Sn^xviii—Ca1—Au^xviii	108.51 (7)
Sn^iii—Au—Ca1	63.4 (2)	Au—Ca1—Au^xviii	124.3 (2)
Ca2—Au—Ca1	78.95 (14)	Au^xix—Ca1—Au^xviii	88.43 (13)
Au^iv—Au—Ca1	129.44 (6)	Au^xii—Ca1—Au^xviii	88.43 (13)
Ca2^v—Au—Ca1	69.50 (12)	Au^xx—Ca1—Au^xviii	124.3 (2)
Ca2^vi—Au—Ca1	131.5 (4)	Sn^xv—Ca1—Au^ii	75.1 (2)
Ca1^vii—Au—Ca1	90.57 (14)	Sn^xvi—Ca1—Au^ii	48.12 (15)
Sn^i—Au—Ca1^viii	61.51 (5)	Sn^iii—Ca1—Au^ii	48.12 (15)
Sn^ii—Au—Ca1^viii	61.51 (5)	Sn^xvii—Ca1—Au^ii	75.1 (2)
Sn^iii—Au—Ca1^viii	166.45 (12)	Sn^ii—Ca1—Au^ii	108.51 (7)
Ca2—Au—Ca1^viii	69.0 (2)	Sn^xviii—Ca1—Au^ii	163.9 (3)
Au^iv—Au—Ca1^viii	62.31 (10)	Au—Ca1—Au^ii	88.43 (13)
Ca2^v—Au—Ca1^viii	102.76 (15)	Au^xix—Ca1—Au^ii	124.3 (2)
Ca2^vi—Au—Ca1^viii	102.76 (15)	Au^xii—Ca1—Au^ii	124.3 (2)
Ca1^vii—Au—Ca1^viii	124.3 (2)	Au^xx—Ca1—Au^ii	88.43 (13)
Ca1—Au—Ca1^viii	124.3 (2)	Au^xviii—Ca1—Au^ii	55.4 (2)
Au^ix—Sn—Au^x	118.87 (9)	Au^xii—Ca2—Au	82.5 (3)
Au^ix—Sn—Au^xi	118.23 (5)	Au^xii—Ca2—Au^x	134.46 (13)
Au^x—Sn—Au^xi	118.23 (5)	Au—Ca2—Au^x	93.35 (6)
Au^ix—Sn—Sn^xii	93.75 (6)	Au^xii—Ca2—Au^xxi	93.35 (6)
Au^x—Sn—Sn^xii	93.75 (6)	Au—Ca2—Au^xxi	134.46 (13)
Au^xi—Sn—Sn^xii	104.13 (6)	Au^x—Ca2—Au^xxi	119.4 (4)
Au^ix—Sn—Ca1^xiii	156.94 (10)	Au^xii—Ca2—Au^xxii	93.35 (6)
Au^x—Sn—Ca1^xiii	70.37 (16)	Au—Ca2—Au^xxii	134.46 (13)
Au^xi—Sn—Ca1^xiii	66.55 (19)	Au^x—Ca2—Au^xxii	58.25 (13)
Sn^xii—Sn—Ca1^xiii	63.74 (7)	Au^xxi—Ca2—Au^xxii	91.0 (2)
Au^ix—Sn—Ca1^xi	70.37 (16)	Au^xii—Ca2—Au^ix	134.46 (13)
Au^x—Sn—Ca1^xi	156.94 (10)	Au—Ca2—Au^ix	93.35 (6)
Au^xi—Sn—Ca1^xi	66.55 (19)	Au^x—Ca2—Au^ix	91.0 (2)
Sn^xii—Sn—Ca1^xi	63.74 (7)	Au^xxi—Ca2—Au^ix	58.25 (13)
Ca1^xiii—Sn—Ca1^xi	93.7 (3)	Au^xxii—Ca2—Au^ix	119.4 (4)
Au^ix—Sn—Ca1^viii	65.84 (7)	Au^xii—Ca2—Sn	163.9 (3)
Au^x—Sn—Ca1^viii	65.84 (7)	Au—Ca2—Sn	113.61 (8)
Au^xi—Sn—Ca1^viii	122.06 (18)	Au^x—Ca2—Sn	48.42 (14)
Sn^xii—Sn—Ca1^viii	133.81 (16)	Au^xxi—Ca2—Sn	75.5 (2)
Ca1^xiii—Sn—Ca1^viii	133.07 (11)	Au^xxii—Ca2—Sn	75.5 (2)
Ca1^xi—Sn—Ca1^viii	133.07 (11)	Au^ix—Ca2—Sn	48.42 (14)
Au^ix—Sn—Ca2	64.61 (6)	Au^xii—Ca2—Sn^xii	113.61 (8)
Au^x—Sn—Ca2	64.61 (6)	Au—Ca2—Sn^xii	163.9 (3)
Au^xi—Sn—Ca2	169.01 (14)	Au^x—Ca2—Sn^xii	75.5 (2)
Sn^xii—Sn—Ca2	64.88 (11)	Au^xxi—Ca2—Sn^xii	48.42 (14)
Ca1^xiii—Sn—Ca2	106.53 (16)	Au^xxii—Ca2—Sn^xii	48.42 (14)
Ca1^xi—Sn—Ca2	106.53 (16)	Au^ix—Ca2—Sn^xii	75.5 (2)
Ca1^viii—Sn—Ca2	68.9 (2)	Sn—Ca2—Sn^xii	50.2 (2)
Au^ix—Sn—Ca2^viii	134.14 (13)	Au^xii—Ca2—Sn^xviii	48.58 (11)
Au^x—Sn—Ca2^viii	61.05 (16)	Au—Ca2—Sn^xviii	102.4 (3)
Au^xi—Sn—Ca2^viii	63.2 (2)	Au^x—Ca2—Sn^xviii	164.2 (3)
Sn^xii—Sn—Ca2^viii	131.67 (7)	Au^xxi—Ca2—Sn^xviii	48.51 (4)
Ca1^xiii—Sn—Ca2^viii	68.86 (12)	Au^xxii—Ca2—Sn^xviii	108.36 (8)
Ca1^xi—Sn—Ca2^viii	129.7 (4)	Au^ix—Ca2—Sn^xviii	89.12 (6)
Ca1^viii—Sn—Ca2^viii	75.76 (15)	Sn—Ca2—Sn^xviii	123.4 (3)
Ca2—Sn—Ca2^viii	123.4 (3)	Sn^xii—Ca2—Sn^xviii	89.22 (13)
Au^ix—Sn—Ca2^xiv	61.05 (16)	Au^xii—Ca2—Sn^i	102.4 (3)
Au^x—Sn—Ca2^xiv	134.14 (13)	Au—Ca2—Sn^i	48.58 (11)
Au^xi—Sn—Ca2^xiv	63.2 (2)	Au^x—Ca2—Sn^i	48.51 (4)
Sn^xii—Sn—Ca2^xiv	131.67 (7)	Au^xxi—Ca2—Sn^i	164.2 (3)
Ca1^xiii—Sn—Ca2^xiv	129.7 (4)	Au^xxii—Ca2—Sn^i	89.12 (6)
Ca1^xi—Sn—Ca2^xiv	68.86 (12)	Au^ix—Ca2—Sn^i	108.36 (8)
Ca1^viii—Sn—Ca2^xiv	75.76 (15)	Sn—Ca2—Sn^i	89.22 (13)
Ca2—Sn—Ca2^xiv	123.4 (3)	Sn^xii—Ca2—Sn^i	123.4 (3)
Ca2^viii—Sn—Ca2^xiv	86.54 (14)	Sn^xviii—Ca2—Sn^i	145.5 (4)
Sn^xv—Ca1—Sn^xvi	52.52 (15)	Au^xii—Ca2—Sn^ii	102.4 (3)
Sn^xv—Ca1—Sn^iii	117.1 (4)	Au—Ca2—Sn^ii	48.58 (11)
Sn^xvi—Ca1—Sn^iii	93.7 (3)	Au^x—Ca2—Sn^ii	108.36 (8)
Sn^xv—Ca1—Sn^xvii	93.7 (3)	Au^xxi—Ca2—Sn^ii	89.12 (6)
Sn^xvi—Ca1—Sn^xvii	117.1 (4)	Au^xxii—Ca2—Sn^ii	164.2 (3)
Sn^iii—Ca1—Sn^xvii	52.52 (15)	Au^ix—Ca2—Sn^ii	48.51 (4)
Sn^xv—Ca1—Sn^ii	133.07 (11)	Sn—Ca2—Sn^ii	89.22 (13)
Sn^xvi—Ca1—Sn^ii	94.03 (5)	Sn^xii—Ca2—Sn^ii	123.4 (3)
Sn^iii—Ca1—Sn^ii	94.03 (5)	Sn^xviii—Ca2—Sn^ii	83.34 (14)
Sn^xvii—Ca1—Sn^ii	133.07 (11)	Sn^i—Ca2—Sn^ii	86.55 (14)
Sn^xv—Ca1—Sn^xviii	94.03 (5)	Au^xii—Ca2—Sn^xxiii	48.58 (11)
Sn^xvi—Ca1—Sn^xviii	133.07 (11)	Au—Ca2—Sn^xxiii	102.4 (3)
Sn^iii—Ca1—Sn^xviii	133.07 (11)	Au^x—Ca2—Sn^xxiii	89.12 (6)
Sn^xvii—Ca1—Sn^xviii	94.03 (5)	Au^xxi—Ca2—Sn^xxiii	108.36 (7)
Sn^ii—Ca1—Sn^xviii	87.6 (3)	Au^xxii—Ca2—Sn^xxiii	48.51 (4)
Sn^xv—Ca1—Au	163.2 (3)	Au^ix—Ca2—Sn^xxiii	164.2 (3)
Sn^xvi—Ca1—Au	113.27 (9)	Sn—Ca2—Sn^xxiii	123.4 (3)
Sn^iii—Ca1—Au	50.09 (5)	Sn^xii—Ca2—Sn^xxiii	89.22 (13)
Sn^xvii—Ca1—Au	85.44 (6)	Sn^xviii—Ca2—Sn^xxiii	86.55 (14)
Sn^ii—Ca1—Au	48.85 (10)	Sn^i—Ca2—Sn^xxiii	83.34 (14)
Sn^xviii—Ca1—Au	102.8 (3)	Sn^ii—Ca2—Sn^xxiii	145.5 (4)

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