Distribution and Ionic Diffusion Path of Silver in γ-Ag8GeTe6: A Temperature Dependent Anharmonic Single Crystal Structure Study
✍ Scribed by F. Boucher; M. Evain; R. Brec
- Publisher
- Elsevier Science
- Year
- 1993
- Tongue
- English
- Weight
- 668 KB
- Volume
- 107
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
The localization and diffusion of silver species in the high temperature allotropic form (\gamma) - (\mathrm{Ag}{8} \mathrm{GeTe}{6}) (space group (F \overline{4} 3 \mathrm{~m}, a=1156.56(4) \mathrm{pm}, Z=4) ) is revisited from temperature dependent (\mathrm{X})-ray data with the aid of refinements including anharmonic thermal motions (Gram-Charlier expansion of the structure factor). (\gamma-\mathrm{Ag}{8} \mathrm{GeTe}{6}) is built upon the stacking of (\mathrm{GeTe}_{4}) tetrahedral units and free tellurium atoms that manages five different tetrahedral sites available for silver ions. A coherent silver distribution over the voids is evidenced by testing three models corresponding to different tensor orders for the alomic displacement parameters (ADP). Three diffusion paths between the preponderant silver sites are revealed by means of joint probability density functions (jpdf) and it is shown through the temperature dependence of those jpdf that the silver disorder is of the positional type. 1993 Academic Press. Inc.