Electrical susceptibilities of KNbO₃ by molecular dynamics simulations using a shell model

We performed molecular dynamics simulations of KNbO₃ using an isotropic shell model by Sepliarsky et al. The anisotropies and the temperature dependence of the experimental susceptibilities of KNbO₃ were found to be reproduced qualitatively in this model. The densities of probabilities of the local polarizations are more widely distributed around their average values compared to those for the previous shell model result of BaTiO₃. This leads to larger fluctuations of the total dipole moments of the MD cell and to larger susceptibilities than the previous results. The dynamical Nb–O chain structures for the cubic phase as well as for the tetragonal phase in the ab plane and for the orthorhombic phase in the c direction were predicted also by this model.