Developing a force field for the Ba1−xCaxZrO3 ferroelectric alloy: Prediction of a ferroelectric superlattice structure

In this study, we develop a classical interatomic potential for the ${\mathrm{Ba}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{ZrO}}_{3}$ alloy based on the bond-valence theory. The bond-valence model enables rapid and large-scale molecular dynamics simulations of alloys with variable compositions. Molecular dynamics simulations based on this force field can reproduce the experimentally observed composition-dependent dielectric responses and lattice constants very well, indicating the validity and robustness of this force field. Based on molecular dynamics simulations, we demonstrate that ${\mathrm{Ba}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{ZrO}}_{3}$ can adopt a ferroelectric phase under a tensile strain, while the ${\mathrm{Ba}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{ZrO}}_{3}$ solid solution under zero strain is paraelectric. In addition, we find that strain can invoke a phase transition from antiferroelectric to ferroelectric in the ${\mathrm{BaZrO}}_{3}/{\mathrm{CaZrO}}_{3}$ superlattice. These results successfully explain previous experimental results and first-principles calculations. This interatomic potential provides a powerful tool for simulating the physical properties of perovskite alloys at nanoscale and thus has great significance in understanding the underlying physical mechanisms and designing functional materials.