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Figure 5

Temperature dependence of (a) the a and b lattice parameters, with a grey dashed line showing the linear fit of the tetragonal a lattice parameter over the P4bm region, extrapolated into the Ama2 region, and (b) the c lattice parameter. Below the ferroelastic transition, the lattice parameters are transposed onto the tetragonal parent structure setting, i.e. a = aorth/[\sqrt 2], b = borth/(2[\sqrt 2]) and c = corth/2. (c) Spontaneous strain as defined in equation (1)[link], with a grey dashed line from a Landau fit with a critical exponent β of 0.32 (Aamlid et al., 2020BB1) and a red star marking the strain from the DFT calculation. (d) Value of the [00l] exponential coefficient accounting for the asymmetric peak shape, demonstrating that the peak shape is a result of the ferroelectric domain structure.


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APPLIED

CRYSTALLOGRAPHY
ISSN: 1600-5767
Volume 56| Part 5| October 2023| Pages 1456-1465

https://doi.org/10.1107/S1600576723006969
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