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Figure 6
Modulation of the volume of the tetrahedral T site. VT,d(t) is the volume calculated using equation (1)[link] from the modulated coordinates of the relevant oxygen atoms. VT,r(t) is calculated using equation (2)[link]. The discrepancy indicates that the initial occupational modulation functions of Al2 and Si2 are not in agreement with the observed variation of VT,d(t). Corrected modulation functions were calculated using equation (3)[link] so that the expected volume [V_{T,r}^\# (t)] and observed volume VT,d(t) of the tetrahedron are consistent.

IUCrJ
Volume 5| Part 4| July 2018| Pages 497-509
ISSN: 2052-2525
https://doi.org/10.1107/S2052252518007467