Acta Cryst. (2009). E65, i15 [ doi:10.1107/S1600536809004991 ]
Single crystals of octaiodine henacosarsenic pentacosagermanium were grown by chemical transport reactions. The structure is isotypic with the analogous clathrates-I. In this structure, the statistically occupied clathrand atoms (As,Ge)46 form bonds in a distorted tetrahedral coordination and their arrangement can define two polyhedra of different sizes; one is an (As,Ge)20 pentagonal dodecahedron, and the other is an (As,Ge)24 tetrakaidecahedron. The guest atom (iodine) resides inside these polyhedra with site symmetry m3 (Wyckoff position 2a) and 
2m (Wyckoff position 6d), respectively.
Les monocristaux de I8As21Ge25 ont été élaborés par transport en phase vapeur à partir d'un mélange stoechiométrique des éléments purs. Le mélange est chauffé dans un tube en quartz scellé pendant 4 jours à 1133 K. Le composé obtenu en fin de réaction est constitué de cristaux stables de forme cubique.
La structure a été déterminée par isotypie aux clathrates-I dans le groupe d'espace Pm3n avec une occupation statistique des sites 6c, 16i et 24k par les atomes de germanium et d'arsenic. Tous les sites mixtes Ge/As ont été affinés avec une contrainte d'occupation totale égale à l'unité; donnant enfin d'affinement la formulation I8As21Ge25 dont la composition atomique [I(at.%) = 14.81, As(at.%) = 38.88, Ge(at.%) = 46.3] est proche de celle déduite par analyse chimique au MEB [I(at.%) = 14.10, As(at.%) = 41.48, Ge(at.%) = 44.41].
Data collection: KappaCCD Software (Nonius, 1998); cell refinement: KappaCCD Software (Nonius, 1998); data reduction: DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: coordinates taken from analogous clathrates-I (Reference?); program(s) used to refine structure: JANA2000 (Petříček & Dušek, 2000); molecular graphics: GRETEP (Laugier & Bochu, 2002); software used to prepare material for publication: JANA2000 (Petříček & Dušek, 2000).
![[Figure 1]](./br2095fig1thm.gif)
| Fig. 1. Projection de la structure de I8As21Ge25 sur le plan (100) montrant les atomes d'Iode (en rouge); d'Arsenic (en bleu) et de Germanium (en gris), avec un déplacement des ellipsoīdes à 90% de probabilité. |
| I8As21Ge25 | Z = 1 |
| Mr = 4403 | F000 = 1917 |
| Cubic, Pm3n | Dx = 6.143 (1) Mg m−3 |
| Hall symbol: -P 4n 2 3 | Mo Kα radiation λ = 0.71069 Å |
| a = 10.5963 (6) Å | Cell parameters from 25 reflections |
| b = 10.5963 (5) Å | θ = 6.1–38.0º |
| c = 10.5963 (8) Å | µ = 34.30 mm−1 |
| α = 90º | T = 293 K |
| β = 90º | Cubic, colourless |
| γ = 90º | 0.08 × 0.07 × 0.04 mm |
| V = 1189.77 (13) Å3 |
| Nonius KappaCCD diffractometer | 606 independent reflections |
| Radiation source: fine-focus sealed tube | 454 reflections with I > 3σ(I) |
| Monochromator: graphite | Rint = 0.064 |
| T = 293 K | θmax = 38.0º |
| φ scans | θmin = 6.1º |
| Absorption correction: Gaussian (JANA2000; Petříček & Dušek, 2000) | h = −17→18 |
| Tmin = 0.137, Tmax = 0.330 | k = −12→10 |
| 5499 measured reflections | l = −10→17 |
| Refinement on F | 3 restraints |
| R[F2 > 2σ(F2)] = 0.030 | Weighting scheme based on measured s.u.'s w = 1/[σ2(F) + 0.0001F2] |
| wR(F2) = 0.037 | (Δ/σ)max = 0.0001 |
| S = 1.75 | Δρmax = 2.48 e Å−3 |
| 606 reflections | Δρmin = −3.60 e Å−3 |
| 15 parameters | Extinction correction: none |
| I8As21Ge25 | γ = 90º |
| Mr = 4403 | V = 1189.77 (13) Å3 |
| Cubic, Pm3n | Z = 1 |
| a = 10.5963 (6) Å | Mo Kα |
| b = 10.5963 (5) Å | µ = 34.30 mm−1 |
| c = 10.5963 (8) Å | T = 293 K |
| α = 90º | 0.08 × 0.07 × 0.04 mm |
| β = 90º |
| Nonius KappaCCD diffractometer | 606 independent reflections |
| Absorption correction: Gaussian (JANA2000; Petříček & Dušek, 2000) | 454 reflections with I > 3σ(I) |
| Tmin = 0.137, Tmax = 0.330 | Rint = 0.064 |
| 5499 measured reflections |
| R[F2 > 2σ(F2)] = 0.030 | 15 parameters |
| wR(F2) = 0.037 | 3 restraints |
| S = 1.75 | Δρmax = 2.48 e Å−3 |
| 606 reflections | Δρmin = −3.60 e Å−3 |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors are based on F, with F set to zero for negative F2. The threshold expression of F2 > n*σ(F2) is used only for calculating R-factors etc. and is not relevant to the choice of reflections for refinement. The program used for refinement, Jana2000, uses the weighting scheme based on the experimental expectations, see _refine_ls_weighting_details, that does not force S to be one. Therefore the values of S are usually larger then the ones from the SHELX program. |
| x | y | z | Uiso*/Ueq | Occ. (<1) | |
| I1 | 0 | 0 | 0 | 0.01086 (12) | |
| I2 | 0.25 | 0.5 | 0 | 0.01537 (14) | |
| Ge3 | 0 | 0.31029 (6) | 0.11761 (6) | 0.01180 (15) | 0.971 (4) |
| As3 | 0 | 0.31029 (6) | 0.11761 (6) | 0.01180 (15) | 0.029 (4) |
| As2 | 0.18337 (4) | 0.18337 (4) | 0.18337 (4) | 0.01082 (8) | 0.900 (4) |
| Ge2 | 0.18337 (4) | 0.18337 (4) | 0.18337 (4) | 0.01082 (8) | 0.100 (4) |
| As1 | 0.25 | 0 | 0.5 | 0.0144 (2) | 0.966 (8) |
| Ge1 | 0.25 | 0 | 0.5 | 0.0144 (2) | 0.034 (8) |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| I1 | 0.0109 (2) | 0.0109 (2) | 0.0109 (2) | 0 | 0 | 0 |
| I2 | 0.0110 (3) | 0.0176 (2) | 0.0176 (2) | 0 | 0 | 0 |
| Ge3 | 0.0112 (3) | 0.0129 (3) | 0.0113 (3) | 0 | 0 | −0.0009 (2) |
| As3 | 0.0112 (3) | 0.0129 (3) | 0.0113 (3) | 0 | 0 | −0.0009 (2) |
| As2 | 0.01082 (14) | 0.01082 (14) | 0.01082 (14) | −0.00079 (13) | −0.00079 (13) | −0.00079 (13) |
| Ge2 | 0.01082 (14) | 0.01082 (14) | 0.01082 (14) | −0.00079 (13) | −0.00079 (13) | −0.00079 (13) |
| As1 | 0.0152 (5) | 0.0140 (3) | 0.0140 (3) | 0 | 0 | 0 |
| Ge1 | 0.0152 (5) | 0.0140 (3) | 0.0140 (3) | 0 | 0 | 0 |
| I1—Ge3 | 3.5161 (7) | I2—Ge3 | 3.5513 (4) |
| I1—Ge3i | 3.5161 (7) | I2—Ge3xvi | 3.5513 (4) |
| I1—Ge3ii | 3.5161 (7) | I2—Ge3xvii | 3.5513 (4) |
| I1—Ge3iii | 3.5161 (7) | I2—Ge3v | 3.5513 (4) |
| I1—Ge3iv | 3.5161 (7) | I2—Ge3xviii | 3.5513 (4) |
| I1—Ge3v | 3.5161 (7) | I2—Ge3xix | 3.5513 (4) |
| I1—Ge3vi | 3.5161 (7) | I2—Ge3xx | 3.5513 (4) |
| I1—Ge3vii | 3.5161 (7) | I2—Ge3xxi | 3.5513 (4) |
| I1—Ge3viii | 3.5161 (7) | I2—As1xxii | 3.7464 (2) |
| I1—Ge3ix | 3.5161 (7) | I2—As1xxiii | 3.7464 (2) |
| I1—Ge3x | 3.5161 (7) | I2—As1xxiv | 3.7464 (2) |
| I1—Ge3xi | 3.5161 (7) | I2—As1xxv | 3.7464 (2) |
| I1—As2 | 3.3655 (4) | Ge3—Ge3v | 2.4925 (9) |
| I1—As2i | 3.3655 (4) | Ge3—As2 | 2.4636 (6) |
| I1—As2xii | 3.3655 (4) | Ge3—As2xiii | 2.4636 (6) |
| I1—As2xiii | 3.3655 (4) | Ge3—As1xxv | 2.4513 (7) |
| I1—As2iv | 3.3655 (4) | As2—As2xiii | 3.8862 (6) |
| I1—As2v | 3.3655 (4) | As2—As2v | 3.8862 (6) |
| I1—As2xiv | 3.3655 (4) | As2—As2xv | 3.8862 (6) |
| I1—As2xv | 3.3655 (4) | As2—As2xxvi | 2.4457 (6) |
| Ge3—I1—Ge3i | 180 | As2xiii—I1—As2i | 109.471 (10) |
| Ge3—I1—Ge3ii | 70.644 (10) | As2xiii—I1—As2xii | 180 |
| Ge3—I1—Ge3iii | 109.356 (10) | As2xiii—I1—As2iv | 70.529 (10) |
| Ge3—I1—Ge3iv | 138.482 (15) | As2xiii—I1—As2v | 109.471 (10) |
| Ge3—I1—Ge3vi | 70.644 (10) | As2xiii—I1—As2xiv | 70.529 (10) |
| Ge3—I1—Ge3vii | 109.356 (10) | As2xiii—I1—As2xv | 109.471 (10) |
| Ge3—I1—Ge3viii | 70.644 (10) | As2iv—I1—As2 | 109.471 (10) |
| Ge3—I1—Ge3ix | 109.356 (10) | As2iv—I1—As2i | 70.529 (10) |
| Ge3—I1—Ge3x | 70.644 (10) | As2iv—I1—As2xii | 109.471 (10) |
| Ge3—I1—Ge3xi | 109.356 (10) | As2iv—I1—As2xiii | 70.529 (10) |
| Ge3—I1—As2i | 138.117 (9) | As2iv—I1—As2v | 180 |
| Ge3—I1—As2xii | 138.117 (9) | As2iv—I1—As2xiv | 109.471 (10) |
| Ge3—I1—As2iv | 109.587 (11) | As2iv—I1—As2xv | 70.529 (10) |
| Ge3—I1—As2v | 70.413 (11) | As2v—I1—As2 | 70.529 (10) |
| Ge3—I1—As2xiv | 70.413 (11) | As2v—I1—As2i | 109.471 (10) |
| Ge3—I1—As2xv | 109.587 (11) | As2v—I1—As2xii | 70.529 (10) |
| Ge3i—I1—Ge3 | 180 | As2v—I1—As2xiii | 109.471 (10) |
| Ge3i—I1—Ge3ii | 109.356 (10) | As2v—I1—As2iv | 180 |
| Ge3i—I1—Ge3iii | 70.644 (10) | As2v—I1—As2xiv | 70.529 (10) |
| Ge3i—I1—Ge3v | 138.482 (15) | As2v—I1—As2xv | 109.471 (10) |
| Ge3i—I1—Ge3vi | 109.356 (10) | As2xiv—I1—As2 | 109.471 (10) |
| Ge3i—I1—Ge3vii | 70.644 (10) | As2xiv—I1—As2i | 70.529 (10) |
| Ge3i—I1—Ge3viii | 109.356 (10) | As2xiv—I1—As2xii | 109.471 (10) |
| Ge3i—I1—Ge3ix | 70.644 (10) | As2xiv—I1—As2xiii | 70.529 (10) |
| Ge3i—I1—Ge3x | 109.356 (10) | As2xiv—I1—As2iv | 109.471 (10) |
| Ge3i—I1—Ge3xi | 70.644 (10) | As2xiv—I1—As2v | 70.529 (10) |
| Ge3i—I1—As2 | 138.117 (9) | As2xiv—I1—As2xv | 180 |
| Ge3i—I1—As2xiii | 138.117 (9) | As2xv—I1—As2 | 70.529 (10) |
| Ge3i—I1—As2iv | 70.413 (11) | As2xv—I1—As2i | 109.471 (10) |
| Ge3i—I1—As2v | 109.587 (11) | As2xv—I1—As2xii | 70.529 (10) |
| Ge3i—I1—As2xiv | 109.587 (11) | As2xv—I1—As2xiii | 109.471 (10) |
| Ge3i—I1—As2xv | 70.413 (11) | As2xv—I1—As2iv | 70.529 (10) |
| Ge3ii—I1—Ge3 | 70.644 (10) | As2xv—I1—As2v | 109.471 (10) |
| Ge3ii—I1—Ge3i | 109.356 (10) | As2xv—I1—As2xiv | 180 |
| Ge3ii—I1—Ge3iii | 180 | Ge3—I2—Ge3xvi | 83.521 (11) |
| Ge3ii—I1—Ge3iv | 70.644 (10) | Ge3—I2—Ge3xvii | 68.952 (13) |
| Ge3ii—I1—Ge3v | 109.356 (10) | Ge3—I2—Ge3xviii | 162.500 (15) |
| Ge3ii—I1—Ge3vii | 138.482 (15) | Ge3—I2—Ge3xix | 99.156 (11) |
| Ge3ii—I1—Ge3viii | 70.644 (10) | Ge3—I2—Ge3xx | 123.809 (13) |
| Ge3ii—I1—Ge3ix | 109.356 (10) | Ge3—I2—Ge3xxi | 123.809 (13) |
| Ge3ii—I1—Ge3x | 109.356 (10) | Ge3—I2—As1xxii | 158.083 (10) |
| Ge3ii—I1—Ge3xi | 70.644 (10) | Ge3—I2—As1xxiii | 97.307 (9) |
| Ge3ii—I1—As2i | 138.117 (9) | Ge3—I2—As1xxiv | 73.781 (9) |
| Ge3ii—I1—As2xii | 109.587 (11) | Ge3xvi—I2—Ge3 | 83.521 (11) |
| Ge3ii—I1—As2xiii | 70.413 (11) | Ge3xvi—I2—Ge3v | 68.952 (13) |
| Ge3ii—I1—As2iv | 70.413 (11) | Ge3xvi—I2—Ge3xviii | 99.156 (11) |
| Ge3ii—I1—As2v | 109.587 (11) | Ge3xvi—I2—Ge3xix | 162.500 (15) |
| Ge3ii—I1—As2xiv | 138.117 (9) | Ge3xvi—I2—Ge3xx | 123.809 (13) |
| Ge3iii—I1—Ge3 | 109.356 (10) | Ge3xvi—I2—Ge3xxi | 123.809 (13) |
| Ge3iii—I1—Ge3i | 70.644 (10) | Ge3xvi—I2—As1xxii | 97.307 (9) |
| Ge3iii—I1—Ge3ii | 180 | Ge3xvi—I2—As1xxiii | 158.083 (10) |
| Ge3iii—I1—Ge3iv | 109.356 (10) | Ge3xvii—I2—Ge3 | 68.952 (13) |
| Ge3iii—I1—Ge3v | 70.644 (10) | Ge3xvii—I2—Ge3v | 83.521 (11) |
| Ge3iii—I1—Ge3vi | 138.482 (15) | Ge3xvii—I2—Ge3xviii | 123.809 (13) |
| Ge3iii—I1—Ge3viii | 109.356 (10) | Ge3xvii—I2—Ge3xix | 123.809 (13) |
| Ge3iii—I1—Ge3ix | 70.644 (10) | Ge3xvii—I2—Ge3xx | 162.500 (15) |
| Ge3iii—I1—Ge3x | 70.644 (10) | Ge3xvii—I2—Ge3xxi | 99.156 (11) |
| Ge3iii—I1—Ge3xi | 109.356 (10) | Ge3xvii—I2—As1xxii | 97.307 (9) |
| Ge3iii—I1—As2 | 138.117 (9) | Ge3xvii—I2—As1xxiii | 158.083 (10) |
| Ge3iii—I1—As2xii | 70.413 (11) | Ge3xvii—I2—As1xxiv | 73.781 (9) |
| Ge3iii—I1—As2xiii | 109.587 (11) | Ge3v—I2—Ge3xvi | 68.952 (13) |
| Ge3iii—I1—As2iv | 109.587 (11) | Ge3v—I2—Ge3xvii | 83.521 (11) |
| Ge3iii—I1—As2v | 70.413 (11) | Ge3v—I2—Ge3xviii | 123.809 (13) |
| Ge3iii—I1—As2xv | 138.117 (9) | Ge3v—I2—Ge3xix | 123.809 (13) |
| Ge3iv—I1—Ge3 | 138.482 (15) | Ge3v—I2—Ge3xx | 99.156 (11) |
| Ge3iv—I1—Ge3ii | 70.644 (10) | Ge3v—I2—Ge3xxi | 162.500 (15) |
| Ge3iv—I1—Ge3iii | 109.356 (10) | Ge3v—I2—As1xxii | 158.083 (10) |
| Ge3iv—I1—Ge3v | 180 | Ge3v—I2—As1xxiii | 97.307 (9) |
| Ge3iv—I1—Ge3vi | 70.644 (10) | Ge3v—I2—As1xxv | 73.781 (9) |
| Ge3iv—I1—Ge3vii | 109.356 (10) | Ge3xviii—I2—Ge3 | 162.500 (15) |
| Ge3iv—I1—Ge3viii | 109.356 (10) | Ge3xviii—I2—Ge3xvi | 99.156 (11) |
| Ge3iv—I1—Ge3ix | 70.644 (10) | Ge3xviii—I2—Ge3xvii | 123.809 (13) |
| Ge3iv—I1—Ge3x | 109.356 (10) | Ge3xviii—I2—Ge3v | 123.809 (13) |
| Ge3iv—I1—Ge3xi | 70.644 (10) | Ge3xviii—I2—Ge3xix | 83.521 (11) |
| Ge3iv—I1—As2 | 109.587 (11) | Ge3xviii—I2—Ge3xxi | 68.952 (13) |
| Ge3iv—I1—As2i | 70.413 (11) | Ge3xviii—I2—As1xxiii | 73.781 (9) |
| Ge3iv—I1—As2xii | 70.413 (11) | Ge3xviii—I2—As1xxiv | 97.307 (9) |
| Ge3iv—I1—As2xiii | 109.587 (11) | Ge3xviii—I2—As1xxv | 158.083 (10) |
| Ge3iv—I1—As2v | 138.117 (9) | Ge3xix—I2—Ge3 | 99.156 (11) |
| Ge3iv—I1—As2xiv | 138.117 (9) | Ge3xix—I2—Ge3xvi | 162.500 (15) |
| Ge3v—I1—Ge3i | 138.482 (15) | Ge3xix—I2—Ge3xvii | 123.809 (13) |
| Ge3v—I1—Ge3ii | 109.356 (10) | Ge3xix—I2—Ge3v | 123.809 (13) |
| Ge3v—I1—Ge3iii | 70.644 (10) | Ge3xix—I2—Ge3xviii | 83.521 (11) |
| Ge3v—I1—Ge3iv | 180 | Ge3xix—I2—Ge3xx | 68.952 (13) |
| Ge3v—I1—Ge3vi | 109.356 (10) | Ge3xix—I2—As1xxii | 73.781 (9) |
| Ge3v—I1—Ge3vii | 70.644 (10) | Ge3xix—I2—As1xxiv | 158.083 (10) |
| Ge3v—I1—Ge3viii | 70.644 (10) | Ge3xix—I2—As1xxv | 97.307 (9) |
| Ge3v—I1—Ge3ix | 109.356 (10) | Ge3xx—I2—Ge3 | 123.809 (13) |
| Ge3v—I1—Ge3x | 70.644 (10) | Ge3xx—I2—Ge3xvi | 123.809 (13) |
| Ge3v—I1—Ge3xi | 109.356 (10) | Ge3xx—I2—Ge3xvii | 162.500 (15) |
| Ge3v—I1—As2 | 70.413 (11) | Ge3xx—I2—Ge3v | 99.156 (11) |
| Ge3v—I1—As2i | 109.587 (11) | Ge3xx—I2—Ge3xix | 68.952 (13) |
| Ge3v—I1—As2xii | 109.587 (11) | Ge3xx—I2—Ge3xxi | 83.521 (11) |
| Ge3v—I1—As2xiii | 70.413 (11) | Ge3xx—I2—As1xxii | 73.781 (9) |
| Ge3v—I1—As2iv | 138.117 (9) | Ge3xx—I2—As1xxiv | 97.307 (9) |
| Ge3v—I1—As2xv | 138.117 (9) | Ge3xx—I2—As1xxv | 158.083 (10) |
| Ge3vi—I1—Ge3 | 70.644 (10) | Ge3xxi—I2—Ge3 | 123.809 (13) |
| Ge3vi—I1—Ge3i | 109.356 (10) | Ge3xxi—I2—Ge3xvi | 123.809 (13) |
| Ge3vi—I1—Ge3iii | 138.482 (15) | Ge3xxi—I2—Ge3xvii | 99.156 (11) |
| Ge3vi—I1—Ge3iv | 70.644 (10) | Ge3xxi—I2—Ge3v | 162.500 (15) |
| Ge3vi—I1—Ge3v | 109.356 (10) | Ge3xxi—I2—Ge3xviii | 68.952 (13) |
| Ge3vi—I1—Ge3vii | 180 | Ge3xxi—I2—Ge3xx | 83.521 (11) |
| Ge3vi—I1—Ge3viii | 109.356 (10) | Ge3xxi—I2—As1xxiii | 73.781 (9) |
| Ge3vi—I1—Ge3ix | 70.644 (10) | Ge3xxi—I2—As1xxiv | 158.083 (10) |
| Ge3vi—I1—Ge3x | 70.644 (10) | Ge3xxi—I2—As1xxv | 97.307 (9) |
| Ge3vi—I1—Ge3xi | 109.356 (10) | As1xxii—I2—As1xxiii | 90 |
| Ge3vi—I1—As2 | 70.413 (11) | As1xxii—I2—As1xxiv | 120 |
| Ge3vi—I1—As2i | 109.587 (11) | As1xxii—I2—As1xxv | 120 |
| Ge3vi—I1—As2xii | 138.117 (9) | As1xxiii—I2—As1xxii | 90 |
| Ge3vi—I1—As2v | 138.117 (9) | As1xxiii—I2—As1xxiv | 120 |
| Ge3vi—I1—As2xiv | 109.587 (11) | As1xxiii—I2—As1xxv | 120 |
| Ge3vi—I1—As2xv | 70.413 (11) | As1xxiv—I2—As1xxii | 120 |
| Ge3vii—I1—Ge3 | 109.356 (10) | As1xxiv—I2—As1xxiii | 120 |
| Ge3vii—I1—Ge3i | 70.644 (10) | As1xxiv—I2—As1xxv | 90 |
| Ge3vii—I1—Ge3ii | 138.482 (15) | As1xxv—I2—As1xxii | 120 |
| Ge3vii—I1—Ge3iv | 109.356 (10) | As1xxv—I2—As1xxiii | 120 |
| Ge3vii—I1—Ge3v | 70.644 (10) | As1xxv—I2—As1xxiv | 90 |
| Ge3vii—I1—Ge3vi | 180 | I1—Ge3—I2 | 113.887 (13) |
| Ge3vii—I1—Ge3viii | 70.644 (10) | I1—Ge3—I2xvi | 113.887 (13) |
| Ge3vii—I1—Ge3ix | 109.356 (10) | I1—Ge3—Ge3v | 69.24 (2) |
| Ge3vii—I1—Ge3x | 109.356 (10) | I1—Ge3—As2 | 65.785 (17) |
| Ge3vii—I1—Ge3xi | 70.644 (10) | I1—Ge3—As2xiii | 65.785 (17) |
| Ge3vii—I1—As2 | 109.587 (11) | I1—Ge3—As1xxv | 165.85 (3) |
| Ge3vii—I1—As2i | 70.413 (11) | I2—Ge3—I2xvi | 96.479 (16) |
| Ge3vii—I1—As2xiii | 138.117 (9) | I2—Ge3—Ge3v | 69.456 (15) |
| Ge3vii—I1—As2iv | 138.117 (9) | I2—Ge3—As2 | 79.626 (11) |
| Ge3vii—I1—As2xiv | 70.413 (11) | I2—Ge3—As2xiii | 175.25 (2) |
| Ge3vii—I1—As2xv | 109.587 (11) | I2—Ge3—As1xxv | 74.729 (13) |
| Ge3viii—I1—Ge3 | 70.644 (10) | I2xvi—Ge3—I2 | 96.479 (16) |
| Ge3viii—I1—Ge3i | 109.356 (10) | I2xvi—Ge3—Ge3v | 69.456 (15) |
| Ge3viii—I1—Ge3ii | 70.644 (10) | I2xvi—Ge3—As2 | 175.25 (2) |
| Ge3viii—I1—Ge3iii | 109.356 (10) | I2xvi—Ge3—As2xiii | 79.626 (11) |
| Ge3viii—I1—Ge3iv | 109.356 (10) | I2xvi—Ge3—As1xxv | 74.729 (13) |
| Ge3viii—I1—Ge3v | 70.644 (10) | Ge3v—Ge3—As2 | 106.43 (2) |
| Ge3viii—I1—Ge3vi | 109.356 (10) | Ge3v—Ge3—As2xiii | 106.43 (2) |
| Ge3viii—I1—Ge3vii | 70.644 (10) | Ge3v—Ge3—As1xxv | 124.91 (3) |
| Ge3viii—I1—Ge3ix | 180 | As2—Ge3—As2xiii | 104.13 (3) |
| Ge3viii—I1—Ge3x | 138.482 (15) | As2—Ge3—As1xxv | 106.61 (2) |
| Ge3viii—I1—As2i | 138.117 (9) | As2xiii—Ge3—As2 | 104.13 (3) |
| Ge3viii—I1—As2xii | 70.413 (11) | As2xiii—Ge3—As1xxv | 106.61 (2) |
| Ge3viii—I1—As2xiii | 109.587 (11) | I1—As2—Ge3 | 72.332 (17) |
| Ge3viii—I1—As2iv | 138.117 (9) | I1—As2—Ge3ii | 72.332 (17) |
| Ge3viii—I1—As2xiv | 109.587 (11) | I1—As2—Ge3viii | 72.332 (17) |
| Ge3viii—I1—As2xv | 70.413 (11) | I1—As2—As2xiii | 54.736 (9) |
| Ge3ix—I1—Ge3 | 109.356 (10) | I1—As2—As2v | 54.736 (9) |
| Ge3ix—I1—Ge3i | 70.644 (10) | I1—As2—As2xv | 54.736 (9) |
| Ge3ix—I1—Ge3ii | 109.356 (10) | I1—As2—As2xxvi | 180 |
| Ge3ix—I1—Ge3iii | 70.644 (10) | Ge3—As2—Ge3ii | 111.21 (2) |
| Ge3ix—I1—Ge3iv | 70.644 (10) | Ge3—As2—Ge3viii | 111.21 (2) |
| Ge3ix—I1—Ge3v | 109.356 (10) | Ge3—As2—As2v | 73.570 (18) |
| Ge3ix—I1—Ge3vi | 70.644 (10) | Ge3—As2—As2xv | 123.08 (2) |
| Ge3ix—I1—Ge3vii | 109.356 (10) | Ge3—As2—As2xxvi | 107.67 (2) |
| Ge3ix—I1—Ge3viii | 180 | Ge3ii—As2—Ge3 | 111.21 (2) |
| Ge3ix—I1—Ge3xi | 138.482 (15) | Ge3ii—As2—Ge3viii | 111.21 (2) |
| Ge3ix—I1—As2 | 138.117 (9) | Ge3ii—As2—As2xiii | 73.570 (18) |
| Ge3ix—I1—As2xii | 109.587 (11) | Ge3ii—As2—As2v | 123.08 (2) |
| Ge3ix—I1—As2xiii | 70.413 (11) | Ge3ii—As2—As2xxvi | 107.67 (2) |
| Ge3ix—I1—As2v | 138.117 (9) | Ge3viii—As2—Ge3 | 111.21 (2) |
| Ge3ix—I1—As2xiv | 70.413 (11) | Ge3viii—As2—Ge3ii | 111.21 (2) |
| Ge3ix—I1—As2xv | 109.587 (11) | Ge3viii—As2—As2xiii | 123.08 (2) |
| Ge3x—I1—Ge3 | 70.644 (10) | Ge3viii—As2—As2xv | 73.570 (18) |
| Ge3x—I1—Ge3i | 109.356 (10) | Ge3viii—As2—As2xxvi | 107.67 (2) |
| Ge3x—I1—Ge3ii | 109.356 (10) | As2xiii—As2—As2v | 90 |
| Ge3x—I1—Ge3iii | 70.644 (10) | As2xiii—As2—As2xv | 90 |
| Ge3x—I1—Ge3iv | 109.356 (10) | As2xiii—As2—As2xxvi | 125.264 (18) |
| Ge3x—I1—Ge3v | 70.644 (10) | As2v—As2—As2xiii | 90 |
| Ge3x—I1—Ge3vi | 70.644 (10) | As2v—As2—As2xv | 90 |
| Ge3x—I1—Ge3vii | 109.356 (10) | As2v—As2—As2xxvi | 125.264 (18) |
| Ge3x—I1—Ge3viii | 138.482 (15) | As2xv—As2—As2xiii | 90 |
| Ge3x—I1—Ge3xi | 180 | As2xv—As2—As2v | 90 |
| Ge3x—I1—As2 | 109.587 (11) | As2xv—As2—As2xxvi | 125.264 (18) |
| Ge3x—I1—As2i | 70.413 (11) | As2xxvi—As2—As2xiii | 125.264 (18) |
| Ge3x—I1—As2xii | 138.117 (9) | As2xxvi—As2—As2v | 125.264 (18) |
| Ge3x—I1—As2iv | 70.413 (11) | As2xxvi—As2—As2xv | 125.264 (18) |
| Ge3x—I1—As2v | 109.587 (11) | I2xxvii—As1—I2xxviii | 90 |
| Ge3x—I1—As2xv | 138.117 (9) | I2xxvii—As1—I2xxix | 120 |
| Ge3xi—I1—Ge3 | 109.356 (10) | I2xxvii—As1—I2xxx | 120 |
| Ge3xi—I1—Ge3i | 70.644 (10) | I2xxvii—As1—Ge3ii | 66.131 (10) |
| Ge3xi—I1—Ge3ii | 70.644 (10) | I2xxvii—As1—Ge3xxxi | 66.131 (10) |
| Ge3xi—I1—Ge3iii | 109.356 (10) | I2xxvii—As1—Ge3xxx | 79.908 (15) |
| Ge3xi—I1—Ge3iv | 70.644 (10) | I2xxvii—As1—Ge3xxxii | 169.908 (15) |
| Ge3xi—I1—Ge3v | 109.356 (10) | I2xxviii—As1—I2xxvii | 90 |
| Ge3xi—I1—Ge3vi | 109.356 (10) | I2xxviii—As1—I2xxix | 120 |
| Ge3xi—I1—Ge3vii | 70.644 (10) | I2xxviii—As1—I2xxx | 120 |
| Ge3xi—I1—Ge3ix | 138.482 (15) | I2xxviii—As1—Ge3ii | 66.131 (10) |
| Ge3xi—I1—Ge3x | 180 | I2xxviii—As1—Ge3xxxi | 66.131 (10) |
| Ge3xi—I1—As2 | 70.413 (11) | I2xxviii—As1—Ge3xxx | 169.908 (15) |
| Ge3xi—I1—As2i | 109.587 (11) | I2xxviii—As1—Ge3xxxii | 79.908 (15) |
| Ge3xi—I1—As2xiii | 138.117 (9) | I2xxix—As1—I2xxvii | 120 |
| Ge3xi—I1—As2iv | 109.587 (11) | I2xxix—As1—I2xxviii | 120 |
| Ge3xi—I1—As2v | 70.413 (11) | I2xxix—As1—I2xxx | 90 |
| Ge3xi—I1—As2xiv | 138.117 (9) | I2xxix—As1—Ge3ii | 169.908 (15) |
| As2—I1—As2i | 180 | I2xxix—As1—Ge3xxxi | 79.908 (15) |
| As2—I1—As2xii | 109.471 (10) | I2xxix—As1—Ge3xxx | 66.131 (10) |
| As2—I1—As2xiii | 70.529 (10) | I2xxix—As1—Ge3xxxii | 66.131 (10) |
| As2—I1—As2iv | 109.471 (10) | I2xxx—As1—I2xxvii | 120 |
| As2—I1—As2v | 70.529 (10) | I2xxx—As1—I2xxviii | 120 |
| As2—I1—As2xiv | 109.471 (10) | I2xxx—As1—I2xxix | 90 |
| As2—I1—As2xv | 70.529 (10) | I2xxx—As1—Ge3ii | 79.908 (15) |
| As2i—I1—As2 | 180 | I2xxx—As1—Ge3xxxi | 169.908 (15) |
| As2i—I1—As2xii | 70.529 (10) | I2xxx—As1—Ge3xxx | 66.131 (10) |
| As2i—I1—As2xiii | 109.471 (10) | I2xxx—As1—Ge3xxxii | 66.131 (10) |
| As2i—I1—As2iv | 70.529 (10) | Ge3ii—As1—Ge3xxxi | 110.18 (2) |
| As2i—I1—As2v | 109.471 (10) | Ge3ii—As1—Ge3xxx | 109.116 (11) |
| As2i—I1—As2xiv | 70.529 (10) | Ge3ii—As1—Ge3xxxii | 109.116 (11) |
| As2i—I1—As2xv | 109.471 (10) | Ge3xxxi—As1—Ge3ii | 110.18 (2) |
| As2xii—I1—As2 | 109.471 (10) | Ge3xxxi—As1—Ge3xxx | 109.116 (11) |
| As2xii—I1—As2i | 70.529 (10) | Ge3xxxi—As1—Ge3xxxii | 109.116 (11) |
| As2xii—I1—As2xiii | 180 | Ge3xxx—As1—Ge3ii | 109.116 (11) |
| As2xii—I1—As2iv | 109.471 (10) | Ge3xxx—As1—Ge3xxxi | 109.116 (11) |
| As2xii—I1—As2v | 70.529 (10) | Ge3xxx—As1—Ge3xxxii | 110.18 (2) |
| As2xii—I1—As2xiv | 109.471 (10) | Ge3xxxii—As1—Ge3ii | 109.116 (11) |
| As2xii—I1—As2xv | 70.529 (10) | Ge3xxxii—As1—Ge3xxxi | 109.116 (11) |
| As2xiii—I1—As2 | 70.529 (10) | Ge3xxxii—As1—Ge3xxx | 110.18 (2) |
| Symmetry codes: (i) −x, −y, −z; (ii) z, x, y; (iii) −z, −x, −y; (iv) −x, −y, z; (v) x, y, −z; (vi) −z, −x, y; (vii) z, x, −y; (viii) y, z, x; (ix) −y, −z, −x; (x) −y, z, −x; (xi) y, −z, x; (xii) x, −y, −z; (xiii) −x, y, z; (xiv) −x, y, −z; (xv) x, −y, z; (xvi) −x, −y+1, −z; (xvii) −x, −y+1, z; (xviii) −x+1/2, z+1/2, y−1/2; (xix) x+1/2, −z+1/2, −y+1/2; (xx) x+1/2, −z+1/2, y−1/2; (xxi) −x+1/2, z+1/2, −y+1/2; (xxii) −y+1/2, x+1/2, z−1/2; (xxiii) y+1/2, −x+1/2, −z+1/2; (xxiv) z−1/2, −y+1/2, x−1/2; (xxv) −z+1/2, y+1/2, −x+1/2; (xxvi) −y+1/2, −x+1/2, −z+1/2; (xxvii) −y+1/2, x−1/2, z+1/2; (xxviii) y−1/2, −x+1/2, −z+1/2; (xxix) z+1/2, −y+1/2, x+1/2; (xxx) −z+1/2, y−1/2, −x+1/2; (xxxi) z, x, −y+1; (xxxii) −z+1/2, −y+1/2, x+1/2. |
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Les clathrates-I de germanium en particulier ceux encapsulant des halogènes ont connus un regain d'intérêt au cours de ces dernières années, essentiellement en raison de leurs propriétés semiconductrices (Chu et al., 1982) et thermoélectriques très prometteuses (Kishimoto et al., 2006). Les premiers clathrates de ce type synthétisés sont de formulation M8A8Ge38 (M: halogènes, A: P, As, Sb) (Menke & von Schnering, 1973) suivi par l'iodide avec I8Ge46-xIx (x = 8/3) (Nesper et al., 1986). Les structures de ces clathrates ont été déterminées par isotypie aux hydrates de gaz correspondants (Pauling & Marsh, 1952). Dans la structure du composé I8As21Ge25 tous les atomes clathrands (Ge,As)46 forment des chaînes tétraédriques légèrement distordues, le réseau est alors décrit par la juxtaposition de deux types de polyèdres: les dodécaèdres pentagonaux (Ge,As)20 et les tétrakaīdècaèdres (Ge,As)24. Les sommets de ces polyèdres sont occupés par les atomes de germanium et d'arsenic, alors que les atomes d'iode se logent aux centres des cavités formées par ces deux types de polyèdres. Les distances entre atomes clathrands [2.4456 (6)–2.4925 (9) Å] sont légèrement supérieures à celle observées dans la structure germanium type diamant 2.4498 Å, mais comparables à celles obtenues dans I8As8Ge38 [2.4457 (6)–2.4925 (9) Å] (Menke & von Schnering, 1973), ou dans d'autres combinaisons avec le dimère AsGe [2.4457 (6)–2.4925 (9) Å] (Shreeve-Keyer et al., 1997). Les angles de liaisons entre atomes clathrands [104.13 (3)–124.91 (3) °] sont similaires à ceux d'une hybridation sp3 dans la structure germanium type diamant. Enfin, il faut noter que l'agitation thermique (ADP's) autour de l'atome I2 (site 6d) est comparable à celles des autres atomes constituants le clathrate, ce n'est pas le cas de nombreux clathrates au germanium où l'agitation thermique autour de M2 (M: métaux alcalins, Eu) est beaucoup plus large (Nolas et al., 2000).