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New insights on the GeSe x Te 1− x phase diagram from theory and experiment
Author(s) -
Herrmann Markus Guido,
Stoffel Ralf Peter,
Küpers Michael,
Ait Haddouch Mohammed,
Eich Andreas,
Glazyrin Konstantin,
Grzechnik Andrzej,
Dronskowski Richard,
Friese Karen
Publication year - 2019
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520619001847
Subject(s) - isostructural , phase diagram , hexagonal crystal system , crystallography , materials science , diffraction , thermodynamics , phase transition , phase (matter) , diagram , crystal structure , chemistry , physics , mathematics , organic chemistry , optics , statistics
The high‐pressure and low‐temperature behaviour of the GeSe x Te 1− x system ( x = 0, 0.2, 0.5, 0.75, 1) was studied using a combination of powder diffraction measurements and first‐principles calculations. Compounds in the stability field of the GeTe structure type ( x = 0, 0.2, 0.5) follow the high‐pressure transition pathway: GeTe‐I ( R 3 m ) → GeTe‐II (f.c.c.) → GeTe‐III ( Pnma ). The newly determined GeTe‐III structure is isostructural to β‐GeSe, a high‐pressure and high‐temperature polymorph of GeSe. Pressure‐dependent formation enthalpies and stability regimes of the GeSe x Te 1− x polymorphs were studied by DFT calculations. Hexagonal Ge 4 Se 3 Te is stable up to at least 25 GPa. Significant differences in the high‐pressure and low‐temperature behaviour of the GeTe‐type structures and the hexagonal phase are highlighted. The role of Ge…Ge interactions is elucidated using the crystal orbital Hamilton population method. Finally, a sketch of the high‐pressure phase diagram of the system is provided.