Order-disorder, local structure and precursor effects in BaTiO₃

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.

Key Words:

• BaTiO₃:
• ferroelectric transition
• molecular dynamics