Molecular dynamics simulation of the phase transition in LaAlO₃

Abstract

We have used molecular dynamics and lattice statics to study LaAlO₃ in the temperature range 0–1500 K. Short range pair potentials were obtained using the Gordon-Kim¹ approach. The O⁻² ion charge density was stabilized using Watson Sphere potentials ranging from 0.7 to 0.8 Har./e. within this range, a phase transition is found to occur at the temperature reported experimentally (800K), however, we find the ground state to have a tetragonal (Pmnb) structure rather than the observed R3C configuration. It is found that the R3C structure can be stabilized by transferring charge from the O⁻² ion to the La⁺³ ion in the long range potential sums.