Redetermination of the quaternary phase silver dicadmium gallium tetra­sulfide, AgCd₂GaS₄

The structure of AgCd₂GaS₄, known from powder data, has been redetermined by means of single-crystal X-ray diffraction. The structure can be described as a superstructure of wurtzite. All metal atoms are in a slightly distorted tetra­hedral environment formed by the S atoms. The Ag, the Ga and two S atoms are situated on positions with m symmetry, while all other atoms are in general positions.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](a-S) = 0.002 Å
• R factor = 0.038
• wR factor = 0.113
• Data-to-parameter ratio = 28.1

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT094_ALERT_2_C Ratio of Maximum / Minimum Residual Density ....       3.04
PLAT199_ALERT_1_C Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_C Check the Reported _diffrn_ambient_temperature .        293 K

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           32.57
           From the CIF: _reflns_number_total               1237
           Count of symmetry unique reflns          776
           Completeness (_total/calc)            159.41%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured       461
           Fraction of Friedel pairs measured     0.594
           Are heavy atom types Z>Si present        yes

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

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 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
   1 ALERT type 4 Improvement, methodology, query or suggestion

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Computing details

Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT; program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXTL (Bruker, 2004); molecular graphics: BS (Ozawa & Kang, 2004); software used to prepare material for publication: SHELXTL (Bruker, 2004).

silver dicadmium(II) gallium tetrasulfide

Crystal data

AgCd2GaS4	F(000) = 476
Mr = 530.63	Dx = 4.726 Mg m^−3
Orthorhombic, Pmn21	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac -2	Cell parameters from 838 reflections
a = 8.1395 (9) Å	θ = 4.3–35.0°
b = 6.9394 (8) Å	µ = 12.79 mm^−1
c = 6.6014 (7) Å	T = 293 K
V = 372.87 (7) Å^3	Prism, orange
Z = 2	0.05 × 0.03 × 0.03 mm

Data collection

Bruker–Nonius X8 Apex CCD area-detector diffractometer	1237 independent reflections
Radiation source: fine-focus sealed tube	968 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.017
Detector resolution: 25 pixels mm^-1	θmax = 32.6°, θmin = 5.9°
φ scans	h = −6→12
Absorption correction: multi-scan (SADABS; Bruker, 2004)	k = −10→10
Tmin = 0.550, Tmax = 0.679	l = −10→7
3258 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.038	w = 1/[σ^2(Fo^2) + (0.0601P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.113	(Δ/σ)max < 0.001
S = 1.08	Δρmax = 3.09 e Å^−3
1237 reflections	Δρmin = −1.02 e Å^−3
44 parameters	Absolute structure: Flack (1983), 486 Friedel pairs
1 restraint	Absolute structure parameter: 0.13 (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. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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

	x	y	z	Uiso*/Ueq
Ag	0.0000	0.33896 (10)	0.50805 (16)	0.0305 (2)
Cd	0.25226 (4)	0.82638 (6)	0.51089 (8)	0.02250 (19)
Ga	0.5000	0.32571 (10)	0.50781 (19)	0.01077 (18)
S1	0.26431 (17)	0.1725 (2)	0.3949 (4)	0.0187 (4)
S2	0.0000	0.6778 (3)	0.3619 (5)	0.0197 (5)
S3	0.5000	0.6394 (3)	0.3949 (5)	0.0218 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ag	0.0317 (4)	0.0326 (4)	0.0272 (4)	0.000	0.000	0.0059 (6)
Cd	0.0212 (2)	0.0251 (3)	0.0212 (3)	−0.00062 (13)	0.00027 (16)	0.0010 (4)
Ga	0.0118 (3)	0.0123 (4)	0.0083 (4)	0.000	0.000	0.0014 (5)
S1	0.0213 (6)	0.0177 (7)	0.0169 (10)	0.0002 (5)	0.0025 (6)	0.0015 (6)
S2	0.0169 (8)	0.0249 (10)	0.0172 (11)	0.000	0.000	−0.0018 (9)
S3	0.0185 (9)	0.0207 (10)	0.0261 (14)	0.000	0.000	−0.0073 (10)

Geometric parameters (Å, º)

Ag—S2	2.541 (3)	Ga—S1	2.316 (2)
Ag—S1^i	2.5535 (17)	Ga—S1^iv	2.3165 (19)
Ag—S1	2.5535 (17)	Ga—S2^ii	2.338 (4)
Ag—S3^ii	2.558 (3)	S1—Cd^v	2.5232 (19)
Cd—S2	2.4993 (16)	S1—Cd^vi	2.538 (3)
Cd—S3	2.5170 (14)	S2—Ga^vi	2.338 (4)
Cd—S1^iii	2.5232 (19)	S2—Cd^i	2.4993 (15)
Cd—S1^ii	2.538 (3)	S3—Cd^iv	2.5170 (14)
Ga—S3	2.301 (3)	S3—Ag^vi	2.558 (3)
S2—Ag—S1^i	107.90 (7)	Ga—S1—Cd^v	111.79 (9)
S2—Ag—S1	107.90 (7)	Ga—S1—Cd^vi	111.35 (9)
S1^i—Ag—S1	114.81 (10)	Cd^v—S1—Cd^vi	107.69 (8)
S2—Ag—S3^ii	108.95 (9)	Ga—S1—Ag	113.33 (9)
S1^i—Ag—S3^ii	108.58 (8)	Cd^v—S1—Ag	108.00 (7)
S1—Ag—S3^ii	108.58 (8)	Cd^vi—S1—Ag	104.25 (9)
S2—Cd—S3	109.02 (7)	Ga^vi—S2—Cd	113.43 (8)
S2—Cd—S1^iii	107.78 (8)	Ga^vi—S2—Cd^i	113.43 (8)
S3—Cd—S1^iii	111.55 (8)	Cd—S2—Cd^i	110.48 (10)
S2—Cd—S1^ii	110.51 (8)	Ga^vi—S2—Ag	111.72 (11)
S3—Cd—S1^ii	110.35 (8)	Cd—S2—Ag	103.44 (9)
S1^iii—Cd—S1^ii	107.60 (7)	Cd^i—S2—Ag	103.44 (9)
S3—Ga—S1	109.26 (9)	Ga—S3—Cd^iv	112.90 (9)
S3—Ga—S1^iv	109.26 (9)	Ga—S3—Cd	112.90 (9)
S1—Ga—S1^iv	111.82 (10)	Cd^iv—S3—Cd	106.48 (9)
S3—Ga—S2^ii	109.48 (11)	Ga—S3—Ag^vi	112.25 (11)
S1—Ga—S2^ii	108.49 (9)	Cd^iv—S3—Ag^vi	105.87 (9)
S1^iv—Ga—S2^ii	108.49 (9)	Cd—S3—Ag^vi	105.87 (9)

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