Development of a bond-valence molecular-dynamics model for complex oxides

A simple ten-parameter interatomic potential model is described that is capable of accurately reproducing the static and dynamical properties of complex oxides. The accuracy of this model stems from the crystal-chemical bond-valence theory of ionic and covalent bonding. The development of a specific variant of this model for ferroelectric PbTiO3 (PT) is discussed in detail, and comparison of the model is made with density functional theory computations and with experimental data. Bond-valence molecular dynamics (BVMD) simulations for PT show a ferroelectric transition at 575 K. The BVMD model correctly reproduces the mixed order-disorder and displacive phase transition character, the magnitudes of cation displacements in the ferroelectric and paraelectric phases, and the energy of 180 degrees domain walls. The success of this simple and physically motivated model makes the simulation of extended defects tractable in PT and other complex oxides.