A non-centrosymmetric polymorph of Gd₃RuO₇

A new non-centrosymmetric modification has been found for trigadolinium ruthenium hepta­oxide, Gd₃RuO₇, crystallizing in the space group P2₁nb. The structure is composed of infinite single chains of corner-linked [RuO₆] octa­hedra embedded in the [Gd₃O] matrix. The octa­hedra in the P2₁nb modification have two tilt systems about the a and c axes, in contrast to the previously reported Cmcm modification [Bontchev et al. (2000). Phys. Rev. B, 62, 12235-12240], with only one tilt system about the a axis. Changes in the coordination of Gd atoms in the title compound are closely related to the tilting mechanism about the c axis.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](u-O) = 0.009 Å
• R factor = 0.047
• wR factor = 0.035
• Data-to-parameter ratio = 30.4

checkCIF/PLATON results

No syntax errors found



Alert level A
DIFMN02_ALERT_2_A  The minimum difference density is < -0.1*ZMAX*2.00
            _refine_diff_density_min given =    -17.043
            Test value =    -12.800

Author Response: Partly due to local disorder of Gd (see comment section in more detail).

DIFMX01_ALERT_2_A  The maximum difference density is > 0.1*ZMAX*2.00
            _refine_diff_density_max given =     17.860
            Test value =     12.800

Author Response: Partly due to local disorder of Gd (see comment section in more detail).

PLAT097_ALERT_2_A Maximum (Positive) Residual Density ............      17.86 e/A   3

Author Response: Partly due to local disorder of Gd (see comment section in more detail).

PLAT098_ALERT_2_A Minimum (Negative) Residual Density ............     -17.04 e/A   3

Author Response: Partly due to local disorder of Gd (see comment section in more detail).

Alert level B
PLAT111_ALERT_2_B ADDSYM Detects (Pseudo) Centre of Symmetry .....         90 PerFit
PLAT111_ALERT_2_B ADDSYM Detects (Pseudo) Centre of Symmetry .....         90 PerFit
PLAT111_ALERT_2_B ADDSYM Detects (Pseudo) Centre of Symmetry .....         81 PerFit
PLAT111_ALERT_2_B ADDSYM Detects (Pseudo) Centre of Symmetry .....         81 PerFit
PLAT112_ALERT_2_B ADDSYM Detects Additional (Pseudo) Symm. Elem...          m

Alert level C
DIFMN03_ALERT_1_C  The minimum difference density is < -0.1*ZMAX*0.75
            The relevant atom site should be identified.
DIFMX02_ALERT_1_C  The maximum difference density is > 0.1*ZMAX*0.75
            The relevant atom site should be identified.
GOODF01_ALERT_2_C  The least squares goodness of fit parameter lies
            outside the range 0.80 <> 2.00
            Goodness of fit given =      2.706
STRVA01_ALERT_4_C           Flack test results are ambiguous.
           From the CIF: _refine_ls_abs_structure_Flack    0.500
           From the CIF: _refine_ls_abs_structure_Flack_su    0.020
PLAT033_ALERT_2_C Flack Parameter Value Deviates from Zero .......       0.50
PLAT041_ALERT_1_C Calc. and Rep. SumFormula Strings    Differ ....          ?
PLAT045_ALERT_1_C Calculated and Reported Z Differ by ............       0.50 Ratio
PLAT087_ALERT_2_C Unsatisfactory S value (Too High) ..............       2.38
PLAT161_ALERT_4_C Missing or Zero su (esd) on x-coordinate for ...        RU1
PLAT199_ALERT_1_C Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_C Check the Reported _diffrn_ambient_temperature .        293 K
PLAT213_ALERT_2_C Atom Gd4     has ADP max/min Ratio .............       3.40 prolat
PLAT220_ALERT_2_C Large Non-Solvent    O     Ueq(max)/Ueq(min) ...       3.27 Ratio

Alert level G
REFLT03_ALERT_4_G  WARNING: Large fraction of Friedel related reflns may
                     be needed to determine absolute structure
           From the CIF: _diffrn_reflns_theta_max           50.00
           From the CIF: _reflns_number_total               5726
           Count of symmetry unique reflns         6246
           Completeness (_total/calc)             91.67%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured         0
           Fraction of Friedel pairs measured     0.000
           Are heavy atom types Z>Si present        yes

   4 ALERT level A = In general: serious problem
   5 ALERT level B = Potentially serious problem
  13 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   6 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
  14 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   3 ALERT type 4 Improvement, methodology, query or suggestion


checkCIF publication errors

Alert level A
PUBL024_ALERT_1_A The number of authors is greater than 5.
              Please specify the role of each of the co-authors
              for your paper.

Author Response: Role of each of co-authors given by initials are: NI. calculation, manuscript preparation; KH. crystal preparation, data collection; DDB. calculation; HH. data collection, SEM/EDS analysis; TI. crystal preparation; SO. crystal preparation

   1 ALERT level A = Data missing that is essential or data in wrong format
   0 ALERT level G = General alerts. Data that may be required is missing

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S1. Comment

A series of Ln₃MO₇ crystals composed of a trivalent lanthanide (Ln) and pentavalent transition metal (M) oxides is structurally characterized by the presence of infinite single chains of corner-linked [MO₆] octahedra embedded in the matrix of Ln and O atoms. This series has attracted attention in recent decades because of its interesting electric and magnetic properties.

Single crystals of Gd₃RuO₇, a member of the Ln₃MO₇ series, were grown by Bontchev et al. (2000) and reported to crystallize in the orthorhombic space group Cmcm at room temperature. The electric conductivity measurement of the Gd₃RuO₇ ceramic sample revealed the Motto variable-range hopping conduction of localized carriers along the [RuO₆] chains (Bontchev et al., 2000). Harada & Hinatsu (2002) reported the first-order phase transition of Gd₃RuO₇ at 382 K in addition to low-temperature transitions at 9.5 and 15 K. They also suggested a possible appearance of a monoclinic modification below 382 K for Gd₃RuO₇. In the course of a systematic study of the Ln₃RuO₇ series, we encountered a new polymorph of Gd₃RuO₇, which is neither the orthorhombic Cmcm modification nor the predicted monoclinic one. It crystallizes in the non-centrosymmetric space group P2₁nb with a doubled b axis compared with that of the Cmcm modification.

The structure of the P2₁nb modification comprises two crystallographically independent Ru atom sites, Ru1 and Ru2, whereas there is only one Ru site in the Cmcm modification. The [Ru1O₆] and [Ru2O₆] octahedra are connected with each other by sharing corners to form isolated single chains along the c axis, as shown in Fig. 1. The [RuO₆] octahedra are tilted about the a axis with an Ru1—O1—Ru2 angle of 144.1 (6)° and an Ru1—O2—Ru2 angle of 140.2 (6)°, resulting in two different Ru1–Ru2 intermetallic distances of 3.632 (3) and 3.752 (3) Å, respectively. The mean values are very close to those (142.6° and 3.690 Å) reported for the Cmcm modification. In the P2₁nb modification, however, another tilt system exists and distinguishes the two modifications. This second tilt occurs only in [Ru1O₆] octahedra with a magnitude of approximately 13° about the axes close to the c direction. [Ru2O₆] has no such tilt system. The second tilt clearly breaks the pseudo-mirror planes at x ≈ 0 and 1/2, discarding the possibility of the centrosymmetric space group Pmnb for the present polymorph.

The Ru—O bond lengths of the [RuO₆] octahedron in the Cmcm modification do not differ significantly (i.e. 1.948 Å × 2 along the chain and 1.940 Å × 4 for the others). This high regularity breaks down in the P2₁nb modification. Here the Ru—O bond lengths of the double-tilted [Ru1O₆] octahedron are grouped into three (i.e. ~1.90 Å × 2, ~1.95 Å × 2 and ~2.01 Å × 2), while those of the single-tilted [Ru2O₆] octahedron are grouped into two (i.e. ~1.92 Å × 3 and ~1.98 Å × 3). The splitting of the Ru—O bonds suggests that the energy level degeneracy of Ru is removed considerably in the P2₁nb modification compared with that in Cmcm.

The title compound contains six crystallographically independent Gd atoms coordinated by seven O atoms each, with interatomic distances ranging from 2.190 (13) to 2.605 (13) Å (Table 1). Atoms Gd1, Gd2, Gd3 and Gd4 are related to the Gd2 site in the Cmcm modification, while atoms Gd5 and Gd6 are related to the Gd1 site according to the notation given by Bontchev et al. (2000). The Gd1 atom in the Cmcm modification has a coordination number (CN) of 8, with four short Gd—O (2.34 Å) and four long Gd—O (2.72 Å) bonds. In contrast, atoms Gd5 and Gd6 in the P2₁nb modification have a CN of 7, with bond distances distributed in shorter ranges of 2.271 (12)–2.548 (12) Å for Gd5 and 2.339 (11)–2.600 (12) Å for Gd6. On the other hand, atoms Gd1, Gd2, Gd3 and Gd4 in the P2₁nb modification have CN of 7, with Gd—O bond lengths similar to those of Gd2 in the Cmcm modification.

The tilting of the [Ru1O₆] octahedra about the c axis in the P2₁nb modification is closely related to the coordination of Gd5 and Gd6 lying near the same (002) plane, as illustrated in Fig. 2. The dashed lines represent lengths of 3.28–3.68 Å, being much longer than the other six Gd—O bonds (three for each Gd with 2.49–2.60 Å) near the plane. On the other hand, the [RuO₆] octahedra in the Cmcm modification have no tilt about the c axis, as shown in Fig. 3. A l l four long Gd—O bonds observed in this modification lie near the (002) plane with the same length of 2.72 Å.

These facts are suggestive when one considers a possible phase transition between the P2₁nb and Cmcm modifications. The formation of octahedral tilt about the c axis in the P2₁nb modification can be described by three steps: (1) systematic small displacements of atoms Gd5 and Gd6 along the direction close relative to the b axis, (2) bond breaking of Gd—O, i.e. Ru1—O—Gd → Ru1—O···Gd (two breaks per [Ru1O₆] octahedron), and (3) small rotation of [Ru1O₆] octahedra about the c axis in order to balance with the two missing Gd—O bonds near the (002) plane. These three steps are geometrically connected to each other and probably occur simultaneously in reality. Therefore it is less meaningful to persist their sequence or the cause/effect relation. However, it is noteworthy that several different structures could be derived from the transition depending on the direction of Gd atom displacement vectors if they are energetically comparable to those that occur in the ideal P2₁nb modification.

Actually we have observed rather large residual electron densities of about +/-17 e Å⁻³ in the direction of the b axis near atoms Gd5 and Gd6. This suggests a possible existence of local disorder of Gd atoms in the crystal structure. In addition, the structure refinement always suffered from the presence of inversion twins with nearly equal volumes. This may suggest an occurrence of any systematic misorientations of the Gd displacements near the composition plane of the twins.

Bontchev et al. (2000) grew crystals of the Cmcm modification by cooling the melt from 1573 to 1273 K at the rate of 1 K h⁻¹ using the same SrCl₂ flux as we did. On the other hand, we grew the crystals by cooling the melt from 1373 to 973 K at a rate of 5 K h⁻¹ with subsequent cooling in the switched-off furnace. This suggests that the present P2₁nb polymorph might be a low-temperature modification with respect to the Cmcm polymorph. The decrease in the CN of Gd5 and Gd6 of the P2₁nb modification from 8 to 7, and a resultant shrinkage of the mean Gd—O bond length, is conformable with this assumption. Further studies to investigate the possible high temperature phase transition of the compound are being in progress.

The present structure belongs to the noncentrosymmetric space group P2₁nb which is polar along the a axis. The [Gd₃O] matrix is supposed to be much insulative compared with the conductive [RuO₆] chains along the c axis. Thus the crystal may be a candidate for a ferroelectric with a spontaneous polarization along the a axis.

S2. Experimental

Crystals were grown by the flux method. The reagent grade powders of Gd₂O₃ (Wako Pure Chemical Industries Ltd., 078–04562, 3.56 mmol), RuO₂ (Japan Pure Chemical Co., 083278, 2.38 mmol) and SrCl₂ flux (Wako Wako Pure Chemical Industries, Ltd., 197–04205, 21.39 mmol) were mixed together, placed in a 30 ml platinum crucible and heated in air to 1373 K in 12 h. The crucible was then kept at that temperature for 6 h, cooled to 973 K at 5 K h⁻¹, and then cooled to room temperature in the switched-off furnace. The product was leached out with warm water to dissolve the flux. The yield was 95.7% in weight. The crystals are black with dimensions of 10–100 µm. Most crystals grown in the present experiment had the shape of a parallelepiped prism elongated along the c axis. The side faces of the prism were composed of {120} and the top and bottom of {101}. Considering the number and strength of bonds that intersect the crystal faces, it is reasonable to assume that the {120} side faces are a set of planes running through the [Gd₃O] matrix. No heavy elements other than Gd and Ru were found by energy dispersive spectroscopy (Jeol, JSM-6100) attached to the scanning electron microscope (Jeol, JED-2001). Most crystals had relatively high crystallinity and were identified as the P2₁nb modification.

S3. Refinement

The unit cell was chosen so that the a and c axes correspond to those of the Cmcm modification given by Bontchev et al. (2000). This resulted in a non-standard setting of the space group Pna2₁ (No. 33). The superstructure reflections that double the b axis were relatively strong and easy to discern. The structure was solved by direct methods (Sheldrick, 1997). No reasonable solutions were obtained assuming the centrosymmetric space group Pmnb, which has the same extinction rules as the non-centrosymmetric space group P2₁nb. The refinement of structure models in Pmnb derived from the final P2₁nb model converged with R values higher than 0.12, leaving negative or extraordinarily large ADP values for several atoms. The absence of mirror planes perpendicular to the a axis in the structure was justified from the octahedral tilting as discussed in the Comment. A stoichiometric composition was assumed in the refinement since population analysis resulted in site occupation factors of 0.96 (1)–1.03 (1) for all Gd and Ru atom sites. The x parameter of Ru1 was fixed at 0 to define the origin in the least-squares procedure. Refinements assuming anisotropic displacement parameters for O atoms were tried in vain. The absolute structure parameter (Flack, 1983) was refined to 0.50 (2), suggesting a presence of inversion related twin components with nearly equal volumes in the crystal. This value did not vary significantly over several different crystals sampled from the same batch. The highest peak and the deepest hole in the final difference Fourier map are located 0.53 Å from Gd5 and 0.39 Å from Gd6, respectively.

Computing details

Data collection: RAPID-AUTO (Rigaku, 1999); cell refinement: RAPID-AUTO; data reduction: Xtal3.7.2 DIFDAT SORTRF and ADDREF (Hall et al., 2003); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: Xtal3.7.2 CRYLSQ; molecular graphics: ATOMS (Dowty, 2005); software used to prepare material for publication: Xtal3.7.2 CIFIO.

Figures

	Fig. 1. Structure of the P21nb modification of Gd3RuO7 viewed along the a axis. Ligands of the Ru1O6 (light purple) and Ru2O6 (light green) octahedra are not shown for clarity. The anisotropic displacement parameters of Gd (red), Ru1 (blue) and Ru2 (green) are drawn at the 99% probability level; isotropic displacement parameters of O atoms are drawn at the same level and are given in light blue.
	Fig. 2. Slices of the P21nb modification near the (002) plane with selected Gd—O bond distances. Colour scheme is the same as in Fig. 1.
	Fig. 3. Slices of the Cmcm modification near the (002) plane with selected Gd—O bond distances. Colour scheme is the same as in Fig. 1.

Trigadolinium ruthenium heptaoxide

Crystal data

Gd3O7Ru	F(000) = 2336
Mr = 684.82	Dx = 7.882 Mg m^−3
Orthorhombic, P21nb	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P -2bc 2a	Cell parameters from 11591 reflections
a = 10.644 (5) Å	θ = 3–70°
b = 14.685 (6) Å	µ = 36.58 mm^−1
c = 7.384 (3) Å	T = 293 K
V = 1154.2 (9) Å^3	Prism, black
Z = 8	0.10 × 0.05 × 0.04 mm

Data collection

Rigaku R-AXIS RAPID image-plate diffractometer	3921 reflections with F > 3σ(F)
Detector resolution: 0.1 pixels mm^-1	Rint = 0.062
ω scans	θmax = 50°, θmin = 3.1°
Absorption correction: numerical (NUMABS; Higashi, 2000)	h = −22→22
Tmin = 0.087, Tmax = 0.183	k = −31→31
95408 measured reflections	l = −15→10
5726 independent reflections

Refinement

Refinement on F	Weighting scheme based on measured s.u.'s
Least-squares matrix: full	(Δ/σ)max = 0.001
R[F^2 > 2σ(F^2)] = 0.047	Δρmax = 17.86 e Å^−3
wR(F^2) = 0.035	Δρmin = −17.04 e Å^−3
S = 2.38	Extinction correction: Zachariasen (1967), Eq22 p292 "Cryst. Comp." Munksgaard 1970
3921 reflections	Extinction coefficient: 135 (7)
129 parameters	Absolute structure: Flack (1983)
0 restraints	Absolute structure parameter: 0.50 (2)
0 constraints

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

	x	y	z	Uiso*/Ueq
Gd1	−0.2193 (2)	0.02324 (6)	−0.23773 (9)	0.0041 (4)
Gd2	−0.2309 (2)	0.22229 (7)	0.24574 (10)	0.0056 (5)
Gd3	−0.2819 (2)	0.27495 (7)	−0.25656 (10)	0.0061 (4)
Gd4	−0.2722 (2)	−0.02921 (6)	0.25127 (8)	0.0040 (4)
Gd5	0.0025 (2)	0.38728 (4)	0.00302 (12)	0.0088 (3)
Gd6	−0.0102 (2)	0.36318 (4)	−0.49721 (12)	0.0077 (3)
Ru1	0.00000	0.12357 (10)	−0.0059 (2)	0.0030 (3)
Ru2	−0.00151 (11)	0.12258 (10)	−0.4978 (2)	0.0032 (3)
O1	0.0017 (12)	0.0831 (7)	−0.2500 (9)	0.0049 (18)*
O2	−0.0137 (12)	0.1683 (8)	0.2503 (10)	0.006 (2)*
O3	0.1264 (10)	0.2179 (8)	−0.4561 (15)	0.010 (2)*
O4	−0.3654 (12)	0.1036 (8)	0.2371 (12)	0.005 (2)*
O5	0.1282 (11)	0.0338 (9)	−0.5394 (15)	0.011 (2)*
O6	−0.1317 (13)	0.3812 (9)	−0.2358 (13)	0.006 (2)*
O7	−0.1290 (9)	0.2188 (7)	−0.4572 (13)	0.0053 (16)*
O8	−0.1343 (13)	−0.1408 (8)	0.2631 (12)	0.006 (2)*
O9	−0.1265 (9)	0.0297 (7)	−0.5301 (13)	0.0055 (16)*
O10	−0.3704 (14)	0.1319 (9)	−0.2421 (13)	0.007 (2)*
O11	−0.1056 (9)	0.0177 (6)	0.0324 (13)	0.0060 (16)*
O12	0.1052 (10)	0.2343 (7)	−0.0526 (14)	0.013 (2)*
O13	0.1606 (10)	0.0638 (7)	0.0412 (14)	0.016 (2)*
O14	−0.1465 (9)	0.1939 (6)	−0.0529 (13)	0.0111 (18)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Gd1	0.0037 (5)	0.0041 (3)	0.0046 (4)	0.0016 (3)	−0.0004 (3)	0.0016 (2)
Gd2	0.0035 (5)	0.0060 (3)	0.0073 (5)	0.0014 (3)	0.0000 (2)	0.0004 (2)
Gd3	0.0055 (5)	0.0059 (3)	0.0070 (4)	−0.0003 (3)	0.0016 (2)	0.0004 (2)
Gd4	0.0061 (5)	0.0025 (3)	0.0035 (4)	0.0030 (3)	−0.0014 (2)	−0.0003 (2)
Gd5	0.0077 (3)	0.0139 (3)	0.0047 (2)	0.0053 (3)	0.0009 (3)	0.0017 (3)
Gd6	0.0030 (3)	0.0150 (3)	0.0049 (2)	0.0000 (3)	0.0006 (3)	−0.0013 (3)
Ru1	0.0032 (3)	0.0044 (2)	0.0013 (3)	0.0012 (4)	−0.0001 (4)	−0.0008 (3)
Ru2	0.0042 (3)	0.0023 (2)	0.0030 (3)	−0.0010 (4)	0.0002 (4)	0.0015 (3)

Geometric parameters (Å, º)

Gd1^i—O10^i	2.266 (14)	Gd4—O1^i	2.533 (13)
Gd1^i—O6	2.293 (14)	Gd5—O6	2.271 (12)
Gd1^i—O13^ii	2.318 (11)	Gd5—O8^ii	2.296 (11)
Gd1^i—O11^i	2.334 (10)	Gd5—O10^i	2.334 (12)
Gd1^i—O9^i	2.376 (10)	Gd5—O4	2.418 (11)
Gd1^i—O5	2.458 (12)	Gd5—O9	2.510 (10)
Gd1^i—O1^i	2.513 (13)	Gd5—O12	2.532 (11)
Gd2—O4	2.257 (13)	Gd5—O5	2.548 (12)
Gd2—O8	2.260 (13)	Gd6—O6	2.339 (11)
Gd2—O3	2.303 (11)	Gd6—O10^i	2.343 (12)
Gd2—O12	2.381 (11)	Gd6—O8^ii	2.366 (11)
Gd2—O14	2.417 (10)	Gd6—O4^i	2.368 (11)
Gd2—O2	2.444 (13)	Gd6—O7	2.487 (10)
Gd2—O7	2.448 (10)	Gd6—O11^ii	2.500 (9)
Gd3—O6	2.239 (14)	Gd6—O3	2.600 (12)
Gd3—O10	2.305 (14)	Ru1^ii—O1^ii	1.898 (7)
Gd3—O7	2.350 (10)	Ru1^ii—O14^ii	1.902 (10)
Gd3—O14	2.399 (10)	Ru1^ii—O11^ii	1.939 (9)
Gd3—O3	2.426 (11)	Ru1^ii—O13^ii	1.953 (11)
Gd3—O12^ii	2.498 (11)	Ru1^ii—O12^ii	2.004 (11)
Gd3—O2^ii	2.605 (13)	Ru1^ii—O2^ii	2.008 (8)
Gd4—O4	2.190 (13)	Ru2—O9	1.919 (10)
Gd4—O8	2.202 (13)	Ru2—O1	1.920 (7)
Gd4—O13^i	2.331 (11)	Ru2—O5	1.924 (12)
Gd4—O5^i	2.378 (11)	Ru2—O3	1.977 (11)
Gd4—O9	2.401 (10)	Ru2—O2^ii	1.981 (8)
Gd4—O11	2.496 (9)	Ru2—O7	1.982 (10)
O1^ii—Ru1^ii—O14^ii	90.3 (5)	O12^ii—Ru1^ii—O2^ii	86.4 (5)
O1^ii—Ru1^ii—O11^ii	83.9 (4)	O9—Ru2—O1	85.2 (5)
O1^ii—Ru1^ii—O13^ii	91.1 (5)	O9—Ru2—O5	89.8 (5)
O1^ii—Ru1^ii—O12^ii	94.9 (5)	O9—Ru2—O2^ii	94.5 (5)
O14^ii—Ru1^ii—O11^ii	89.2 (4)	O9—Ru2—O7	92.9 (4)
O14^ii—Ru1^ii—O12^ii	89.2 (4)	O1—Ru2—O5	86.2 (5)
O14^ii—Ru1^ii—O2^ii	86.3 (5)	O1—Ru2—O3	93.1 (5)
O11^ii—Ru1^ii—O13^ii	97.0 (4)	O1—Ru2—O7	94.8 (5)
O11^ii—Ru1^ii—O2^ii	94.7 (4)	O5—Ru2—O3	90.6 (5)
O13^ii—Ru1^ii—O12^ii	84.6 (4)	O5—Ru2—O2^ii	97.3 (5)
O13^ii—Ru1^ii—O2^ii	92.4 (5)

Symmetry codes: (i) x+1/2, −y+1/2, z+1/2; (ii) x, y+1/2, −z+1/2.