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Figure 4
Symmetry-related phase transitions in Cu2−xSe. (a) The cubic α-structure. Seα (grey, 4a, [m\overline 3m]), Cu1α (blue, 8c, [\bar 43m]), Cu2α (red, 32f, 3m). (b) Intermediate structure with symmetry reduction leading to split Cu positions. Se (grey, 3a, [\overline 3m]), Cu1α (blue, 6c, 3m), Cu2aα (red, 6c, 3m), Cu2bα (green, 18h, m). (c) The β-Cu2−xSe structure after symmetry lowering from the intermediate phase. Seβ (grey, 6c, 3m), Cu1aβ (blue, 6c, 3m), Cu1bβ (red, 6c, 3m), Cu2β (green, 18h, m). The transparent yellow atoms are the resulting vacant sites.

IUCrJ
Volume 4| Part 4| July 2017| Pages 476-485
ISSN: 2052-2525
https://doi.org/10.1107/S2052252517005553