324914 Application of Bond-Valence Theory for Developing Efficient Interatomic Potential for Oxides
First-principles density functional theory (DFT) calculations have played an important role in enhancing microscopic understanding of intrinsic effects (e.g., compositions and structures) on material properties of oxides.[1-2] For elucidating the changes (dynamics) in material behaviors with extrinsic effects, such as temperature, strain, and electric field, large system sizes and long simulations are necessary. Conventional first-principles methods for large systems and long-time simulations are limited due to their intense computational costs. There is therefore still a strong need to develop accurate and efficient atomistic potential that could reproduce the full dynamical behaviors of metal oxides. [3-9] The development of general atomistic potentials for oxides has proven difficult due to the complex nature of various metal-oxygen bonds.
In this work, we developed a bond-valence model based on the principles of bond-valence and bond-valence vector conservation. [11-12] The relationship between the bond-valence model and the bond-order potential is derived analytically in the framework of a tight-binding model, demonstrating that our model is formally equivalent to the bond-order potential, but is dramatically more efficient computationally. A new energy term, bond-valence vector energy, is introduced into the atomistic model. The force fields for PbTiO3 and BiFeO3 are parameterized respectively.  The new model potential can be applied to both canonical ensemble (NVT) and isobaric-isothermal ensemble (NPT) molecular dynamics (MD) simulations. Our model potential can reproduce the experimental phase transition in NVT MD simulations and also exhibit the experimental sequence of temperature-driven and pressure-driven phase transitions in NPT simulations. We expect that our bond-valence model can be applied to a broad range of inorganic materials.
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