Year: 2026
Type: article
Abstract: 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 $P2_1/c\rightarrow P2_1$ 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.
Source: Physical Review Materials
DOI: 10.1103/q5bn-lhw6
Author: Yongjin Shin
Institution: Dankook University
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
Funder: Dankook University
OpenAlex ID: W7212062696