Cu₂ZnSiS₄

Single crystals of Cu₂ZnSiS₄, dicopper(I) zinc silicon tetrasulfide, have been prepared via high-temperature solid-state synthesis. Cu₂ZnSiS₄ was found to have the wurtz-stannite structure type, like that of Li₂CdGeS₄, Li₂CdSnS₄, and Cu₂CdSiS₄. Each sulfur anion is tetra­hedrally coordinated by two Cu cations, one Si cation, and one Zn cation, forming a three-dimensional honeycomb structure. When viewed along the c axis, the atoms are aligned in rows in which each cation alternates with the sulfur anions.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](S-Si) = 0.002 Å
• R factor = 0.020
• wR factor = 0.051
• Data-to-parameter ratio = 24.5

checkCIF/PLATON results

No syntax errors found



Alert level A
PLAT113_ALERT_2_A ADDSYM Suggests Possible Pseudo/New Space-group.       Pmmn

Author Response: The structure type of Cu~2~ZnSiS~4~ is wurtz-stannite which is noncentrosymmetric that is consistent with the space group Pmn2~1~, see Fig 2.

Alert level B
PLAT029_ALERT_3_B _diffrn_measured_fraction_theta_full Low .......       0.95
PLAT111_ALERT_2_B ADDSYM Detects (Pseudo) Centre of Symmetry .....        100 PerFi
PLAT112_ALERT_2_B ADDSYM Detects Additional (Pseudo) Symm. Elem...          m
PLAT232_ALERT_2_B Hirshfeld Test Diff (M-X)  Zn1    --  S1      ..      27.00 su
PLAT232_ALERT_2_B Hirshfeld Test Diff (M-X)  Zn1    --  S2      ..      19.60 su

Alert level C
PLAT153_ALERT_1_C The su's on the Cell Axes   are Equal (x 100000)         10 Ang.
PLAT232_ALERT_2_C Hirshfeld Test Diff (M-X)  Cu1    --  S1      ..       9.25 su
PLAT232_ALERT_2_C Hirshfeld Test Diff (M-X)  Cu1    --  S3_d    ..       8.25 su
PLAT232_ALERT_2_C Hirshfeld Test Diff (M-X)  Cu1    --  S2_e    ..       8.25 su
PLAT912_ALERT_4_C Missing # of FCF Reflections Above STh/L=  0.600         31
PLAT915_ALERT_3_C Low Friedel Pair Coverage ......................      89.05 Perc.

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           32.85
           From the CIF: _reflns_number_total               1078
           Count of symmetry unique reflns          629
           Completeness (_total/calc)            171.38%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured       449
           Fraction of Friedel pairs measured     0.714
           Are heavy atom types Z>Si present        yes
PLAT792_ALERT_1_G Note: The Model has Chirality at Si1    (Verify)          S
PLAT794_ALERT_5_G Note: Tentative Bond Valency for Zn1     (II)          2.02
PLAT794_ALERT_5_G Note: Tentative Bond Valency for Cu1     (II)          1.91
PLAT917_ALERT_2_G The FCF is likely NOT based on a BASF/TWIN Flack          !

   1 ALERT level A = Most likely a serious problem - resolve or explain
   5 ALERT level B = A potentially serious problem, consider carefully
   6 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   5 ALERT level G = General information/check it is not something unexpected

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   9 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion
   2 ALERT type 5 Informative message, check

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S1. Comment

Cu₂ZnSiS₄ was prepared as crystals via iodine vapor transport reactions as early as 1967 (Nitsche et al., 1967); however, only lattice parameters were reported. Using the same synthetic method to prepare Cu₂ZnSiS₄, Yao et al. reported the infrared spectrum of this compound (Yao et al., 1987). Alternatively Cu₂ZnSiS₄ can be synthesized by grinding stoichiometric amounts of the elements and reacting them in a vibrational mill multiple times during the heating process (Himmrich & Haeuseler, 1991). More recently, the band gap of the title compound has been reported (Levcenco et al., 2010). In this paper, Cu₂ZnSiS₄ was prepared as relatively small single crystals using a simple high-temperature solid-state synthesis.

Cu₂ZnSiS₄ possesses the wurtz-stannite structure type (Schäfer, & Nitsche, 1974) like that of Li₂CdGeS₄, Li₂CdSnS₄ (Lekse et al., 2009), and Cu₂CdSiS₄ (Chapuis & Niggli, 1972). The asymmetric unit can be observed in Figure 1. Cu₂ZnSiS₄ has a diamond-like structure, where every cation is tetrahedrally coordinated with sulfur anions. The bond lengths for M—S range from 2.3170 (7)–2.3426 (7)Å for M=Cu, 2.322 (1)–2.3650 (7)Å for M=Zn, and 2.131 (1)–2.143 (3)Å for M=Si (Table 1). Every MS₄ tetrahedron points in the same direction along the crystallographic b axis rendering the structure noncentrosymmetric (Fig.2). When viewed down the c axis, the ions are aligned in rows where each cation alternates with the sulfur anions (Fig.3).

Recently second harmonic generation for a couple of compounds of this structure type, Li₂CdGeS₄ and Li₂CdSnS₄, have been reported on powder samples (Lekse et al., 2009). Therefore it is of interest to further study Cu₂ZnSiS₄.

Related literature

For synthetic procedures, see: Himmrich & Haeuseler (1991); Nitsche et al. (1967); Yao et al. (1987). For related structures, see: Chapuis & Niggli (1972); Lekse et al. (2008); Lekse et al. (2009); Schäfer & Nitsche (1974). For optical properties, see: Levcenco et al. (2010).

S2. Experimental

Cu₂ZnSiS₄ was prepared via high-temperature solid-state synthesis. Stoichiometric ratios of the elements were weighed and then ground for 30 min in an argon-filled glovebox using an agate mortar and pestle. The sample was placed into a graphite crucible, which was then inserted in a 12 mm outer diameter fused-silica tube. The tube was flame sealed under a vacuum of 10^-3 mbar and transported to a computer-controlled furnace. The sample was heated to 1000°C in 12hrs, held at 1000°C for 168hrs and then cooled at 7.5°C/hr to room temperature. When removed from the furnace, blue rod-like crystals of approximate size 0.13 x 0.07 x 0.6 mm were found under a light microscope.

Computing details

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT (Bruker, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: CrystalMaker (Palmer, 2010); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures

	Fig. 1. Asymetric unit of Cu2ZnSiS4 using 95% probability thermal ellipsoids.
	Fig. 2. Polyhedral view down the b axis of Cu2ZnSiS4 with sulfur anions as the corners of each tetrahedron.
	Fig. 3. Cu2ZnSiS4 viewed along the c axis showing a three-dimensional honeycomb structure where the atoms are aligned in rows with each cation alternating with sulfur anions. Color code: Cu - green, Zn - blue, Si - red, and S - yellow.

dicopper(I) zinc silicon tetrasulfide

Crystal data

Cu2ZnSiS4	F(000) = 332
Mr = 348.78	Dx = 3.964 Mg m^−3
Orthorhombic, Pmn21	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac -2	Cell parameters from 3127 reflections
a = 7.4374 (1) Å	θ = 3.2–32.2°
b = 6.4001 (1) Å	µ = 12.77 mm^−1
c = 6.1394 (1) Å	T = 296 K
V = 292.24 (1) Å^3	Rod, blue
Z = 2	0.13 × 0.07 × 0.06 mm

Data collection

Bruker SMART APEX diffractometer	1078 independent reflections
Radiation source: fine-focus sealed tube	1023 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.021
ϕ and ω scans	θmax = 32.9°, θmin = 3.2°
Absorption correction: multi-scan (SADABS; Sheldrick, 2002)	h = −11→11
Tmin = 0.290, Tmax = 0.500	k = −9→9
5153 measured reflections	l = −9→9

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	w = 1/[σ^2(Fo^2) + (0.0067P)^2 + 0.2702P] where P = (Fo^2 + 2Fc^2)/3
R[F^2 > 2σ(F^2)] = 0.020	(Δ/σ)max < 0.001
wR(F^2) = 0.051	Δρmax = 0.72 e Å^−3
S = 1.14	Δρmin = −1.01 e Å^−3
1078 reflections	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
44 parameters	Extinction coefficient: 0.025 (1)
1 restraint	Absolute structure: Flack (1983), 449 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.02 (1)

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
Cu1	0.24741 (3)	0.17426 (4)	0.33723 (8)	0.0133 (1)
Zn1	0.0000	0.34747 (7)	0.84124 (15)	0.0211 (1)
Si1	0.0000	0.6743 (1)	0.3451 (4)	0.0071 (1)
S1	0.0000	0.3611 (1)	0.4632 (1)	0.0094 (1)
S2	0.0000	0.6784 (1)	0.9961 (2)	0.0089 (2)
S3	0.26269 (8)	0.1724 (1)	−0.0411 (1)	0.0100 (1)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0141 (1)	0.0135 (1)	0.0125 (2)	−0.0007 (1)	−0.0008 (1)	0.0000 (2)
Zn1	0.0235 (2)	0.0210 (2)	0.0191 (3)	0.000	0.000	−0.0016 (3)
Si1	0.0078 (3)	0.0077 (3)	0.0058 (5)	0.000	0.000	0.0007 (4)
S1	0.0126 (3)	0.0072 (3)	0.0085 (5)	0.000	0.000	0.0011 (4)
S2	0.0099 (3)	0.0104 (3)	0.0064 (6)	0.000	0.000	−0.0001 (3)
S3	0.0089 (2)	0.0101 (3)	0.0110 (5)	−0.0012 (1)	0.0006 (3)	0.0000 (3)

Geometric parameters (Å, º)

Cu1—S2^i	2.3170 (7)	Si1—S3^vi	2.136 (1)
Cu1—S3	2.325 (1)	Si1—S2^vii	2.143 (3)
Cu1—S1	2.3270 (6)	S1—Cu1^viii	2.3270 (6)
Cu1—S3^ii	2.3426 (7)	S2—Si1^iv	2.143 (3)
Zn1—S2	2.322 (1)	S2—Cu1^vi	2.3170 (7)
Zn1—S1	2.322 (1)	S2—Cu1^v	2.3170 (7)
Zn1—S3^iii	2.3650 (7)	S3—Si1^i	2.136 (1)
Zn1—S3^iv	2.3650 (7)	S3—Cu1^ix	2.3426 (7)
Si1—S1	2.131 (1)	S3—Zn1^vii	2.3650 (7)
Si1—S3^v	2.136 (1)
S2^i—Cu1—S3	112.51 (4)	Si1—S1—Zn1	112.05 (8)
S2^i—Cu1—S1	106.98 (3)	Si1—S1—Cu1^viii	111.72 (5)
S3—Cu1—S1	111.92 (4)	Zn1—S1—Cu1^viii	108.24 (4)
S2^i—Cu1—S3^ii	106.09 (4)	Si1—S1—Cu1	111.72 (5)
S3—Cu1—S3^ii	108.38 (3)	Zn1—S1—Cu1	108.24 (4)
S1—Cu1—S3^ii	110.82 (4)	Cu1^viii—S1—Cu1	104.51 (4)
S2—Zn1—S1	112.01 (5)	Si1^iv—S2—Cu1^vi	115.21 (4)
S2—Zn1—S3^iii	107.88 (4)	Si1^iv—S2—Cu1^v	115.21 (4)
S1—Zn1—S3^iii	108.84 (4)	Cu1^vi—S2—Cu1^v	108.34 (5)
S2—Zn1—S3^iv	107.88 (4)	Si1^iv—S2—Zn1	113.46 (6)
S1—Zn1—S3^iv	108.84 (4)	Cu1^vi—S2—Zn1	101.47 (4)
S3^iii—Zn1—S3^iv	111.40 (5)	Cu1^v—S2—Zn1	101.47 (4)
S1—Si1—S3^v	108.68 (7)	Si1^i—S3—Cu1	111.38 (7)
S1—Si1—S3^vi	108.68 (7)	Si1^i—S3—Cu1^ix	110.92 (5)
S3^v—Si1—S3^vi	111.40 (7)	Cu1—S3—Cu1^ix	108.76 (3)
S1—Si1—S2^vii	110.60 (9)	Si1^i—S3—Zn1^vii	111.42 (5)
S3^v—Si1—S2^vii	108.74 (7)	Cu1—S3—Zn1^vii	105.21 (4)
S3^vi—Si1—S2^vii	108.74 (7)	Cu1^ix—S3—Zn1^vii	108.95 (3)

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