Crystal structures of η′′-Cu3+xSi and η′′′-Cu3+xSi

Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials

5 years ago

Crystal structures of η′′-Cu3+xSi and η′′′-Cu3+xSi

Olivier Perez, Mariana Klementová, Cinthia Antunes Corrêa, Lukáš Palatinus, Petr Brázda, Jaromír Kopeček

The binary phase diagram of Cu–Si is unexpectedly complex in the vicinity of Cu3+xSi. The low-temperature region contains three closely related incommensurately modulated phases denoted, in order of increasing temperature of stability, η′′′, η′′ and η′. The structure analysis of η′ has been reported previously [Palatinus et al. (2011). Inorg. Chem.50, 3743]. Here the structure model for the phases η′′ and η′′′ is reported. The structures could be solved in superspace, but no superspace structure model could be constructed due to the complexity of the modulation functions. Therefore, the structures were described in a supercell approximation, which involved a 4 × 4 × 3 supercell for the η′′ phase and a 14 × 14 × 3 supercell for the η′′′ phase. Both structures are very similar and differ only by a subtle symmetry lowering from η′′ to η′′′. A comparison of the structure models of η′′ and η′′′ with the reported structure of η′ suggests that the reported structure model of η′ contains an incorrect assignment of atomic types.The incommensurately modulated structures of η′′-Cu3+xSi and η′′′-Cu3+xSi are described in the superstructure approximation. The structures are compared.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1107/S2052520617006163