Compressible and polarizable ion models parametrized by ab initio calculations represent a promising technique for simulating challenging materials such as oxides. We present a new form of such a model in which the compression and polarization effects are coupled, and the anion-anion interaction is not fixed but dependent on the ion size and polarization. These two effects provide a more physically realistic description of a system, and significantly improve the predictive power of the method. Calculations on magnesium oxide show the elastic constants and other properties to be in good agreement with experiment. The new functional form is part of an ongoing project to develop an empirical model of zirconia, an important oxide for which a satisfactory model has yet to be determined.
