Order-disorder, local structure and precursor effects in BaTiO₃

Abstract

Abstract Interatomic potentials are determined in the framework of the nonlinear oxygen polarizability model to describe the structural behavior of BaTiO3To this purpose, the adiabatic potential is evaluated for different ferroelectric distortions and the model potential parameters are obtained by comparing with LAPW total energy calculations. The phase diagram as a function of temperature is obtained through constant pressure molecular dynamics simulations, and the non-trivial phase sequence is correctly reproduced. Calculations of the pair distribution function indicate that order-disorder is the dominant dynamics at all transitions. Precursor clusters with local polarizations correlated along Ti-O chains are determined to persist several hundreds of degrees above the para-ferroelectric transition.