Metastable polar order and phase competition in Carpy-Galy LaTaO4
Abstract
Carpy-Galy LaTaO4 undergoes a structural sequence linking the antipolar monoclinic P21/c ground state and the polar orthorhombic Cmc21 phase through an incommensurately modulated regime. First-principles calculations identify a metastable polar monoclinic P21 phase as a commensurate intermediate in the phase-transition landscape. As a common subgroup of P21/c and Cmc21, P21 provides a symmetry-connected route between the established polymorphs. Mode-resolved energy surfaces for these symmetry-breaking pathways show that coupling between the respective primary order parameters and an isosymmetric relaxation stabilizes the P21 minimum along both pathways. Consequently, the P21/c→ P21 transformation has a finite energy barrier, while a restricted soft-mode model retains competing P21 and Cmc21 basins over an illustrative range of harmonic stiffness. Lattice-metric and neutron-diffraction comparisons indicate a shared displacement character between the calculated commensurate state and the experimental IC-o modulation, supporting the use of P21 as a commensurate structural reference for IC-o. Finally, composition-dependent energetics suggest chemical routes for tuning polar-antipolar competition.
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BibTeX
@misc{shin2026metastable,
title = {{Metastable polar order and phase competition in Carpy-Galy LaTaO4}},
author = {Yongjin Shin},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.06943},
eprint = {2609.06943},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.06943},
}
RIS
TY - UNPB
TI - Metastable polar order and phase competition in Carpy-Galy LaTaO4
AU - Yongjin Shin
PY - 2026
DA - 2026/10/16
PB - arXiv
DO - 10.48550/arxiv.2609.06943
UR - https://arxiv.org/abs/2609.06943
AB - Carpy-Galy LaTaO_4 undergoes a structural sequence linking the antipolar monoclinic P2_1/c ground state and the polar orthorhombic Cmc2_1 phase through an incommensurately modulated regime. First-principles calculations identify a metastable polar monoclinic P2_1 phase as a commensurate intermediate in the phase-transition landscape. As a common subgroup of P2_1/c and Cmc2_1, P2_1 provides a symmetry-connected route between the established polymorphs. Mode-resolved energy surfaces for these symmetry-breaking pathways show that coupling between the respective primary order parameters and an isosymmetric relaxation stabilizes the P2_1 minimum along both pathways. Consequently, the P2_1/c→ P2_1 transformation has a finite energy barrier, while a restricted soft-mode model retains competing P2_1 and Cmc2_1 basins over an illustrative range of harmonic stiffness. Lattice-metric and neutron-diffraction comparisons indicate a shared displacement character between the calculated commensurate state and the experimental IC-o modulation, supporting the use of P2_1 as a commensurate structural reference for IC-o. Finally, composition-dependent energetics suggest chemical routes for tuning polar-antipolar competition.
ER -