Ferroelectric phase transitions in NaCa-halide perovskites

Abstract

We have used lattice statics and dynamics, as well as molecular dynamics to investigate the possibility of structural phase transitions in NaCaX₃ compounds in which X is one of the halides; F, Cl, Br, I. These simulations were done using 320-ion clusters and ab initio potentials with no adjustable parameters. Our computations lead to the prediction that these compounds all have high temperature phases which are distorted perovskites and that each of them undergoes a phase transition to a polar state, although the structure of the ground state and the direction of the polar axis varies with the size of the halide ion.

Key Words:

• Ferroelectrics
• Perovskites
• lattice statics
• molecular dynamics