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Figure 3
Three distinct M5− displacive modes, derived from the RP parent. (a) M5−(a, 0) antiparallel displacements of adjacent layers along one in-plane axis of the supercell; (b) M5−(a, a) showing anti-parallel displacements of adjacent layers along one in-plane axis of the parent cell; (c) M5−(a,b) allows two different amplitudes of displacement along the in-plane axes of the parent cell. It can be seen that the (a, 0) mode results in layers shifted towards DJ type, (a, a) towards DJ2 type, and (a, b) provides both degrees of freedom. Note that each mode also allows a distortion of the octahedra, which is illustrated in (a) by the differing lengths of the trans-octahedral edges.

IUCrJ
Volume 8| Part 4| July 2021| Pages 485-513
ISSN: 2052-2525
https://doi.org/10.1107/S2052252521005418