Interatomic potentials are determined in the framework of a shell model used to simulate the structural instabilities, dynamical properties, and phase transition sequence of BaTiO 3 . The model is developed from first-principles calculations by mapping the potential energy surface for various ferroelectric distortions. The parameters are obtained by performing a fit of interatomic potentials to this energy surface. Several zero-temperature properties of BaTiO 3 , which are of central importance, are correctly simulated in the framework of our model. The phase diagram as a function of temperature is obtained through constant-pressure molecular dynamics simulations, showing that the non-trivial phase transition sequence of BaTiO 3 is correctly reproduced. The lattice parameters and expansion coefficients for the different phases are in good agreement with experimental data, while the theoretically determined transition temperatures tend to be too small.

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Classical shell-model potentials for describing the complex ferroelectric behaviour of barium titanate and strontium titanate are developed and used to simulate BaxSr1−xTiO3 solid solutions. The temperature versus composition phase diagram is very well described and the local behaviour of the structure and polarization is analysed. It is shown that the ferroelectric properties of the solid solution can be understood in terms of the effects of average density and the local chemical environment. The experimentally observed static dielectric peak broadening around Tc at low x is reproduced in the simulation and seems to be related to the average volume rather than to the local chemical environment.