arXiv subjects

Lan-Tien Hsu

Publications and source records attributed to Lan-Tien Hsu.

3 recordsLinked to original sources

arXiv2026

Competing phases and domain structures of ferroelectric perovskites: the benefit of epitaxial (110) growth

Strain and domain engineering offer powerful routes to control phase and domain stability in ferroelectric thin films. While most studies have focused on (100)-oriented growth, the impact of lower-symmetry orientations remains underexplored. We address this gap in knowledge with first-principles based molecular dynamics simulation for the example of prototypical ferroelectric perovskites under (110) strain. Epitaxial (110) strains may indeed outperform the widely studied (100) orientation, as even modest strain values stabilize a diverse set of metastable nanoscale states with potential high functional tunability. In this regime, the films exhibit multidomain configurations with domain wall normal oriented along the clamped in-plane or the relaxed out-of-plane directions and heterophases in BaTiO$_3$ and KNbO$_3$. Besides, complex superdomain patterns and antiferroelectric-like domains are observed in PbTiO$_3$. These metastable nanoscale configurations may allow for large reversible responses.

cond-mat.mtrl-sci↗

arXiv2025

Efficient local atomic cluster expansion for BaTiO$_3$ close to equilibrium

Barium titanate (BTO) is a representative perovskite oxide that undergoes three first-order ferroelectric phase transitions related to exceptional functional properties. In this work, we develop two atomic cluster expansion (ACE) models for BTO to reproduce fundamental properties of bulk as well as defective BTO phases. The two ACE models do not target full transferability but rather aim to examine the influence of implicit and explicit treatment of long-range Coulomb interactions. We demonstrate that both models describe equally well the temperature induced phase transitions as well as polarization switching due to applied electric field. Even though the parametrizations are based on a limited number of configurations that are mostly not far away from the equilibrium, the ACE models are able to capture also properties of important crystal defects, such as oxygen vacancies, stacking faults and domain walls. A systematic comparison shows that the phase transitions as well as the fundamental properties of the investigated defects can be described with similar accuracy with or without explicit treatment of charges and Coulomb interactions allowing for efficient short-range machine learning potentials.

cond-mat.mtrl-sci↗

arXiv2024

Electric field direction dependence of the electrocaloric effect in BaTiO3

Single-crystalline ferroelectric (FE) perovskites show a large electrocaloric effect at electric field-induced phase transitions, promising for solid-state cooling technologies. However, paraelectric-FE transition temperatures are often too high for practical applications, and lower transitions are underrepresented in literature. Particularly, the role of thermal hysteresis and electric field direction on the caloric response is critical, especially for polycrystalline materials, but not yet fully understood. Using ab initio-based coarse-grained molecular dynamics simulations, we show how transition temperatures depend on the direction of the applied field. Also, we reveal that the choice of electric field direction can reduce thermal hysteresis and can adjust the temperature ranges where large and reversible caloric responses occur. Furthermore, we propose a phenomenological descriptor for the qualitative changes in transition temperature with field direction. This descriptor is valid for both BaTiO3 and PbTiO3, even though both materials show different microscopic electric field coupling. Finally, we identify favorable temperature and texturing conditions for large and reversible caloric responses in polycrystals.

cond-mat.mtrl-sci↗