Atomistic modelling of BaTiO3 based on first-principles calculations

Interatomic potentials are determined in the framework of a shell model use d to simulate the structural instabilities, dynamical properties, and phase transition sequence of BaTiO3. The model is developed from first-principle s calculations by mapping the potential energy surface for various ferroele ctric distortions. The parameters are obtained by performing a fit of inter atomic potentials to this energy surface. Several zero-temperature properti es of BaTiO3, which are of central importance, are correctly simulated in t he framework of our model. The phase diagram as a function of temperature i s obtained through constant-pressure molecular dynamics simulations, showin g that the non-trivial phase transition sequence of BaTiO3 is correctly rep roduced. The lattice parameters and expansion coefficients for the differen t phases are in good agreement with experimental data, while the theoretica lly determined transition temperatures tend to be too small.