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Figure 2
(a), (b) The distorted AN structure induced by the T4+ mode only, viewed along (a) the c axis and (b) the a axis. (c), (d) The distorted AN structure induced by the H2 mode only, viewed along (c) the a axis and (d) the b axis. The +/− signs on the right in panel (d) show the clockwise/anticlockwise rotation, respectively, of the right-hand column of octahedra around the a axis. (e) The distorted structure induced by the Λ3 mode only, and (f) that of the Γ4− mode only. The black arrows in panel (e) show the off-centre Nb5+ and Ag+ cation displacements, while the red arrows in panels (e) and (f) indicate the local spontaneous polarization. The horizontal dashed red lines represent antiphase boundaries for octahedral rotation around the a axis in panel (d) and cation displacements along the c axis in panel (e).

IUCrJ
Volume 6| Part 4| July 2019| Pages 740-750
ISSN: 2052-2525
https://doi.org/10.1107/S2052252519007711