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arXiv · 2310.18421

Absence of high pressure ground state re-entrant ferroelectricity in PbTiO$_3$

R. E. Cohen·Yangzheng Lin·Muhtar Ahart·Russell J. Hemley
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Abstract

We study ferroelectricity in the classic perovskite ferroelectric PbTiO$_3$ to high pressures with density functional theory (DFT) and experimental diamond-anvil techniques. We use second harmonic generation (SHG) spectroscopy to detect lack of inversion symmetry. Consistent with early understanding and experiments, we find that ferroelectricity disappears at moderate pressures. However, DFT computations show that the disappearance arises from the overtaking of zone boundary instabilities, and not from the squeezing out of the off-centering ferroelectric displacements with pressure, as previously thought. Moreover, at high pressures the distorted perovskite phases are metastable with respect to a new dense centrosymmetric post-perovskite phase with P$2_1/m$ symmetry and 8-coordinated Ti, which becomes stable at about 70 GPa.

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R. E. Cohen, Yangzheng Lin, Muhtar Ahart, Russell J. Hemley. 2023-10-27. Absence of high pressure ground state re-entrant ferroelectricity in PbTiO$_3$. https://arxiv.org/abs/2310.18421

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