Dielectric properties of BaTiO3 by molecular dynamics simulations using a shell model

We calculated the susceptibilities of BaTiO₃ by molecular dynamics (MD) simulations using an isotropic shell model of Tinte et al. (S. Tinte, M.G. Stachiotti, S.R. Phillpot, M. Sepliarsky, D. Wolf, and R.L. Migoni, Ferroelectric properties of BaxSr1-xTiO₃ solid solutions obtained by molecular dynamics simulation. J Phys Condens Matter, 16, pp. 3495–3506, 2004). The anisotropy of the susceptibilities was reproduced for the ferroelectric phases. However, the susceptibilities were significantly underestimated with respect to experimental ones especially for the a direction. The densities of probabilities of the local polarisations in this model for both the macroscopically polarised and not polarised directions were strongly localised around their average values, leading to the small fluctuation of the total dipole moment of the MD cell and resulting in the underestimated susceptibilities. The order–disorder character was found to be stronger in this model than in the effective Hamiltonian based on the first principles calculations.