Acta Cryst. (2007). E63, i187 [ doi:10.1107/S1600536807048593 ]
Single crystals of tricerium hemimagnesium germanium heptasulfide were obtained by sintering a Ce2S3-MgS-GeS2 mixture. The compound crystallizes in the space group P63 and is isotypic with other Ln3T0.5XS7 phases (Ln = lanthanide, T = divalent transition metal, and X = Si or Ge). The slightly distorted trigonal [MgS6] antiprism has 3 symmetry, with the Mg position half-occupied. The latter position correlates well with the disordered Ag2 positions in the Ln3Ag1-![[delta]](http://journals.iucr.org/logos/entities/delta_rmgif.gif)
SnS7 (Ln = La, Ce; = 0.18-0.19) and Ln3Ag1-SiS7 (Ln = La-Nd, Sm; = 0.10-0.23) structures. The present single-crystal study confirms the previous refinement from powder data, but with all displacement parameters refined anisotropically.
Single crystals of the title compound were grown by fusion of the elemental constituents (Alfa Aesar; purity > 99.9%wt) in the stoichiometric ratio of Ce:Ge:Mg:S = 3:1:0.5:7 in evacuated silica ampoules. In order to avoid reaction of magnesium with SiO2, the ampoule was covered with graphite. The ampoule was heated in a tube furnace with a heating rate of 30 K/h to 1420 K and were kept at this temperature for 3 h. It was then cooled down slowly (10 K/h) to 870 K and annealed at this temperature for further 240 h and finally quenched in cold water. The obtained red crystals had a prismatic habit with a maximal length of 0.3 mm.
The site occupancy factor for Mg atom was constrained (s.o.f.=0.5) during refinement in order to satisfy the charge balance requirement. Results of single-crystal reinvestigation of Ce3Mg0.5GeS7 agree well with those reported on the basis of the powder diffraction study (lattice parameters: a = 10.262 (2), c = 7.7849 (7) Å; Huch et al., 2006), but with improved precision on atomic coordinates and interatomic distances.
Data collection: CrysAlis (Oxford Diffraction, 2006); cell refinement: CrysAlis (Oxford Diffraction, 2006); data reduction: CrysAlis (Oxford Diffraction, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 2005); software used to prepare material for publication: publCIF (Westrip, 2007).
| Ce3Mg0.50GeS7 | Z = 2 |
| Mr = 729.53 | F000 = 648 |
| Hexagonal, P63 | Dx = 4.605 Mg m−3 |
| Hall symbol: P 6c | Mo Kα radiation λ = 0.71073 Å |
| a = 10.2626 (15) Å | Cell parameters from 919 reflections |
| b = 10.2626 (15) Å | θ = 4.2–29.6º |
| c = 5.7679 (12) Å | µ = 16.91 mm−1 |
| α = 90º | T = 293 (2) K |
| β = 90º | Prism, red |
| γ = 120º | 0.13 × 0.11 × 0.08 mm |
| V = 526.09 (15) Å3 |
| Kuma KM-4 diffractometer with CCD area detector | 945 independent reflections |
| Radiation source: fine-focus sealed tube | 919 reflections with I > 2σ(I) |
| Monochromator: graphite | Rint = 0.032 |
| Detector resolution: 1024x1024 with blocks 2x2, 33.133pixel/mm pixels mm-1 | θmax = 29.6º |
| T = 293(2) K | θmin = 4.2º |
| ω scans | h = −14→13 |
| Absorption correction: numerical (CrysAlis; Oxford Diffraction, 2006) | k = −13→14 |
| Tmin = 0.175, Tmax = 0.367 | l = −7→8 |
| 7638 measured reflections |
| Refinement on F2 | Secondary atom site location: difference Fourier map |
| Least-squares matrix: full | w = 1/[σ2(Fo2) + (0.0105P)2] where P = (Fo2 + 2Fc2)/3 |
| R[F2 > 2σ(F2)] = 0.013 | (Δ/σ)max = 0.001 |
| wR(F2) = 0.022 | Δρmax = 0.53 e Å−3 |
| S = 1.01 | Δρmin = −0.56 e Å−3 |
| 945 reflections | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
| 38 parameters | Extinction coefficient: 0.0111 (3) |
| 1 restraint | Absolute structure: Flack (1983), 409 Friedel pairs |
| Primary atom site location: structure-invariant direct methods | Flack parameter: −0.017 (12) |
| Ce3Mg0.50GeS7 | γ = 120º |
| Mr = 729.53 | V = 526.09 (15) Å3 |
| Hexagonal, P63 | Z = 2 |
| a = 10.2626 (15) Å | Mo Kα |
| b = 10.2626 (15) Å | µ = 16.91 mm−1 |
| c = 5.7679 (12) Å | T = 293 (2) K |
| α = 90º | 0.13 × 0.11 × 0.08 mm |
| β = 90º |
| Kuma KM-4 diffractometer with CCD area detector | 945 independent reflections |
| Absorption correction: numerical (CrysAlis; Oxford Diffraction, 2006) | 919 reflections with I > 2σ(I) |
| Tmin = 0.175, Tmax = 0.367 | Rint = 0.032 |
| 7638 measured reflections |
| R[F2 > 2σ(F2)] = 0.013 | 1 restraint |
| wR(F2) = 0.022 | Δρmax = 0.53 e Å−3 |
| S = 1.01 | Δρmin = −0.56 e Å−3 |
| 945 reflections | Absolute structure: Flack (1983), 409 Friedel pairs |
| 38 parameters | Flack parameter: −0.017 (12) |
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 > 2sigma(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. |
| x | y | z | Uiso*/Ueq | Occ. (<1) | |
| Ce | 0.357264 (14) | 0.231380 (14) | 0.23296 (6) | 0.00788 (5) | |
| Ge1 | 0.6667 | 0.3333 | 0.81575 (8) | 0.00757 (11) | |
| Mg1 | 0.0000 | 0.0000 | 0.4694 (10) | 0.0089 (6) | 0.50 |
| S1 | 0.6667 | 0.3333 | 0.4400 (2) | 0.0098 (3) | |
| S2 | 0.08688 (7) | 0.24688 (7) | 0.21849 (17) | 0.01013 (12) | |
| S3 | 0.52030 (8) | 0.10633 (8) | 0.96601 (13) | 0.00851 (14) |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Ce | 0.00658 (7) | 0.00734 (7) | 0.00894 (7) | 0.00289 (5) | 0.00076 (9) | −0.00015 (10) |
| Ge1 | 0.00819 (15) | 0.00819 (15) | 0.0063 (2) | 0.00409 (8) | 0.000 | 0.000 |
| Mg1 | 0.0063 (7) | 0.0063 (7) | 0.0141 (16) | 0.0031 (4) | 0.000 | 0.000 |
| S1 | 0.0115 (4) | 0.0115 (4) | 0.0064 (6) | 0.00574 (18) | 0.000 | 0.000 |
| S2 | 0.0080 (3) | 0.0102 (3) | 0.0123 (3) | 0.0046 (2) | −0.0012 (4) | 0.0000 (4) |
| S3 | 0.0067 (3) | 0.0077 (3) | 0.0099 (3) | 0.0026 (3) | −0.0008 (3) | 0.0004 (3) |
| Ce—S2i | 2.8567 (7) | Ge1—S3ix | 2.2216 (8) |
| Ce—S2 | 2.8589 (7) | Mg1—S2x | 2.655 (3) |
| Ce—S3ii | 2.8972 (8) | Mg1—S2 | 2.655 (3) |
| Ce—S2iii | 2.9720 (12) | Mg1—S2i | 2.655 (3) |
| Ce—S3iv | 2.9941 (8) | Mg1—S2iii | 2.650 (3) |
| Ce—S3v | 3.0351 (8) | Mg1—S2xi | 2.650 (3) |
| Ce—S1 | 3.0465 (7) | Mg1—S2xii | 2.650 (3) |
| Ce—S2vi | 3.1298 (12) | Mg1—Mg1xi | 2.8839 (6) |
| Ce—Mg1 | 3.498 (2) | Mg1—Mg1vii | 2.8840 (6) |
| Ce—Mg1vii | 3.562 (3) | Mg1—Cei | 3.498 (2) |
| Ge1—S1 | 2.1671 (14) | Mg1—Cex | 3.498 (2) |
| Ge1—S3viii | 2.2216 (8) | Mg1—Cexii | 3.562 (3) |
| Ge1—S3 | 2.2216 (8) | ||
| S2i—Ce—S2 | 84.84 (3) | S2xi—Mg1—Cei | 55.79 (3) |
| S2i—Ce—S3ii | 142.14 (3) | S2xii—Mg1—Cei | 126.72 (3) |
| S2—Ce—S3ii | 108.53 (2) | S2x—Mg1—Ce | 124.03 (19) |
| S2i—Ce—S2iii | 77.34 (2) | S2—Mg1—Ce | 53.26 (5) |
| S2—Ce—S2iii | 77.31 (2) | S2i—Mg1—Ce | 53.21 (5) |
| S3ii—Ce—S2iii | 139.37 (2) | S2iii—Mg1—Ce | 55.79 (3) |
| S2i—Ce—S3iv | 73.94 (2) | S2xi—Mg1—Ce | 126.72 (3) |
| S2—Ce—S3iv | 140.79 (3) | S2xii—Mg1—Ce | 126.77 (3) |
| S3ii—Ce—S3iv | 73.92 (3) | Cei—Mg1—Ce | 105.79 (10) |
| S2iii—Ce—S3iv | 127.211 (19) | S2x—Mg1—Cex | 53.26 (5) |
| S2i—Ce—S3v | 144.09 (2) | S2—Mg1—Cex | 53.21 (5) |
| S2—Ce—S3v | 71.09 (2) | S2i—Mg1—Cex | 124.03 (19) |
| S3ii—Ce—S3v | 72.593 (16) | S2iii—Mg1—Cex | 126.72 (3) |
| S2iii—Ce—S3v | 71.74 (2) | S2xi—Mg1—Cex | 126.77 (3) |
| S3iv—Ce—S3v | 140.464 (19) | S2xii—Mg1—Cex | 55.79 (3) |
| S2i—Ce—S1 | 115.164 (15) | Cei—Mg1—Cex | 105.79 (10) |
| S2—Ce—S1 | 150.03 (2) | Ce—Mg1—Cex | 105.79 (10) |
| S3ii—Ce—S1 | 70.08 (2) | S2x—Mg1—Cexii | 127.74 (2) |
| S2iii—Ce—S1 | 85.33 (3) | S2—Mg1—Cexii | 58.29 (3) |
| S3iv—Ce—S1 | 68.84 (2) | S2i—Mg1—Cexii | 127.69 (2) |
| S3v—Ce—S1 | 80.388 (17) | S2iii—Mg1—Cexii | 52.29 (5) |
| S2i—Ce—S2vi | 74.81 (2) | S2xi—Mg1—Cexii | 121.89 (19) |
| S2—Ce—S2vi | 74.78 (2) | S2xii—Mg1—Cexii | 52.33 (5) |
| S3ii—Ce—S2vi | 75.01 (2) | Cei—Mg1—Cexii | 177.67 (17) |
| S2iii—Ce—S2vi | 141.90 (2) | Ce—Mg1—Cexii | 75.523 (7) |
| S3iv—Ce—S2vi | 68.07 (2) | Cex—Mg1—Cexii | 75.523 (7) |
| S3v—Ce—S2vi | 121.248 (19) | Ge1—S1—Ceviii | 113.08 (2) |
| S1—Ce—S2vi | 130.18 (3) | Ge1—S1—Ceix | 113.08 (2) |
| Mg1—Ce—Mg1vii | 48.212 (11) | Ceviii—S1—Ceix | 105.63 (3) |
| S1—Ge1—S3viii | 112.96 (2) | Ge1—S1—Ce | 113.08 (2) |
| S1—Ge1—S3 | 112.96 (2) | Ceviii—S1—Ce | 105.63 (3) |
| S3viii—Ge1—S3 | 105.77 (3) | Ceix—S1—Ce | 105.63 (3) |
| S1—Ge1—S3ix | 112.96 (2) | Mg1—S2—Mg1vii | 65.87 (2) |
| S3viii—Ge1—S3ix | 105.77 (3) | Mg1—S2—Cex | 78.69 (2) |
| S3—Ge1—S3ix | 105.77 (3) | Mg1vii—S2—Cex | 80.52 (2) |
| S2x—Mg1—S2 | 93.12 (15) | Mg1—S2—Ce | 78.65 (2) |
| S2x—Mg1—S2i | 93.12 (15) | Mg1vii—S2—Ce | 80.48 (2) |
| S2—Mg1—S2i | 93.12 (15) | Cex—S2—Ce | 154.89 (3) |
| S2x—Mg1—S2iii | 179.8 (2) | Mg1—S2—Cev | 142.58 (11) |
| S2—Mg1—S2iii | 86.754 (14) | Mg1vii—S2—Cev | 76.72 (11) |
| S2i—Mg1—S2iii | 86.754 (14) | Cex—S2—Cev | 95.74 (2) |
| S2x—Mg1—S2xi | 86.754 (14) | Ce—S2—Cev | 95.69 (2) |
| S2—Mg1—S2xi | 179.8 (2) | Mg1—S2—Cexii | 75.51 (11) |
| S2i—Mg1—S2xi | 86.754 (14) | Mg1vii—S2—Cexii | 141.38 (11) |
| S2iii—Mg1—S2xi | 93.37 (15) | Cex—S2—Cexii | 92.36 (2) |
| S2x—Mg1—S2xii | 86.754 (14) | Ce—S2—Cexii | 92.32 (2) |
| S2—Mg1—S2xii | 86.754 (14) | Cev—S2—Cexii | 141.90 (2) |
| S2i—Mg1—S2xii | 179.8 (2) | Ge1—S3—Cexiii | 91.41 (3) |
| S2iii—Mg1—S2xii | 93.37 (15) | Ge1—S3—Cexiv | 88.90 (2) |
| S2xi—Mg1—S2xii | 93.37 (15) | Cexiii—S3—Cexiv | 110.96 (3) |
| S2x—Mg1—Cei | 53.21 (5) | Ge1—S3—Ceiii | 122.24 (3) |
| S2—Mg1—Cei | 124.03 (19) | Cexiii—S3—Ceiii | 140.35 (3) |
| S2i—Mg1—Cei | 53.26 (5) | Cexiv—S3—Ceiii | 91.63 (2) |
| S2iii—Mg1—Cei | 126.77 (3) |
| Symmetry codes: (i) −x+y, −x, z; (ii) −x+y+1, −x+1, z−1; (iii) y, −x+y, z+1/2; (iv) x, y, z−1; (v) x−y, x, z−1/2; (vi) y, −x+y, z−1/2; (vii) −x, −y, z−1/2; (viii) −y+1, x−y, z; (ix) −x+y+1, −x+1, z; (x) −y, x−y, z; (xi) −x, −y, z+1/2; (xii) x−y, x, z+1/2; (xiii) −y+1, x−y, z+1; (xiv) x, y, z+1. |
| Ce—S2i | 2.8567 (7) | Ce—S1 | 3.0465 (7) |
| Ce—S2 | 2.8589 (7) | Ce—S2vi | 3.1298 (12) |
| Ce—S3ii | 2.8972 (8) | Ge1—S1 | 2.1671 (14) |
| Ce—S2iii | 2.9720 (12) | Ge1—S3 | 2.2216 (8) |
| Ce—S3iv | 2.9941 (8) | Mg1—S2 | 2.655 (3) |
| Ce—S3v | 3.0351 (8) | Mg1—S2iii | 2.650 (3) |
| Symmetry codes: (i) −x+y, −x, z; (ii) −x+y+1, −x+1, z−1; (iii) y, −x+y, z+1/2; (iv) x, y, z−1; (v) x−y, x, z−1/2; (vi) y, −x+y, z−1/2. |
Brandenburg, K. (2005). DIAMOND. Release 3.0e. Crystal Impact GbR, Bonn, Germany.
Daszkiewicz, M., Gulay, L. D., Pietraszko, A. & Shemet, V. Ya. (2007a). J. Solid State Chem. 180, 2053–2060.
Daszkiewicz, M., Gulay, L. D., Pietraszko, A. & Shemet, V. Ya. (2007b). J. Alloys Compd. In the press.
Flack, H. D. (1983). Acta Cryst. A39, 876–881.
Huch, M. R., Gulay, L. D. & Olekseyuk, I. D. (2006). J. Alloys Compd. 424, 114–118.
Oxford Diffraction (2006). CrysAlis Version 1.171.32.6. Oxford Diffraction Ltd, Abingdon, Oxfordshire, England.
Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.
Westrip, S. P. (2007). publCIF. In preparation.
![[Figure 1]](./wm2149fig1thm.gif)
The formation of the quaternary compound Ce3Mg0.5GeS7 has been investigated very recently during phase formation studies in the quasi-ternary Ce2S3—MgS-GeS2 system at 870 K, and its crystal structure was originally refined from X-ray powder diffraction data (Huch et al., 2006). To obtain more accurate results we have now re-investigated the structure from single-crystal data.
The unit cell and coordination polyhedra of the Ce, Mg and Ge atoms in the structure of the title compound are shown in Fig. 1. The Ce atoms are surrounded by 8 S atoms which form distorted bi-capped trigonal prisms. The magnesium position is half-occupied and is in the centre of a trigonal antiprism which has 3 symmetry. This position correlates well with the disordered Ag2 position in the structures of Ln3Ag1-δSnS7 (Ln = La, Ce; δ = 0.18–0.19) (Daszkiewicz et al., 2007a) and Ln3Ag1-δSiS7 (Ln = La—Nd, Sm; δ = 0.10–0.23) (Daszkiewicz et al., 2007b). The Ge atom is situated on a position with 3 symmetry, and is surrounded tetrahedrally by four S atoms with one short and three longer Ge—S bonds.