2025/03/05 by Fan, Di, Zhu, Tianyuan, Liu, Shi
#Computational Physics (physics.comp-ph) #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci)
paper · doi:10.48550/arxiv.2503.03433
The antipolar Pbcn phase of HfO2 has been suggested to play an important role in the phase transition and polarization switching mechanisms in ferroelectric hafnia. In this study, we perform a comprehensive benchmark of density functional theory (DFT) calculations and deep potential molecular dynamics (DPMD) simulations to investigate the thermodynamic stability and phase transition behavior of hafnia, with a particular focus on the relationship between the Pbcn and ferroelectric Pca21 phases. Our results reveal significant discrepancies in the predicted stability of the Pbcn phase relative to the Pca21 phase across different exchange-correlation functionals. Notably, the PBE and hybrid HSE06 functionals exhibit consistent trends, which diverge from the predictions of the PBEsol and SCAN functionals. For a given density functional, temperature-driven phase transitions predicted by DFT-based quasi-harmonic free energy calculations aligns with finite-temperature MD simulations using a deep potential trained on the same density functional. Specifically, the PBE functional predicts a transition from Pca21 to Pbcn with increasing temperature, while PBEsol predicts a transition from Pca21 to P42/nmc. A particularly striking and reassuring finding is that under fixed mechanical boundary conditions defined by the ground-state structure of Pca21, all functionals predict consistent relative phase stabilities and comparable switching barriers as well as domain wall energies. These findings underscore the unique characteristics of the Pbcn phase in influencing phase transitions and switching mechanisms in ferroelectric hafnia.