Molecular-dynamics simulation of ferroelectric clusters.

Abstract

Stoichiometric clusters with zero dipole moment are constructed from the perovskite structure by cleaving along the 8 〈111〉 and 6 〈100〉 planes positioned equal distances from an origin midway between the two cations. The procedure is used to form clusters of ${\mathrm{NaCaF}}_{3}$, a hypothetical material which is predicted to be ferroelectric in the rigid-ion approximation. Results of molecular-dynamics calculations are reported for several clusters ranging in size from N=35 to 5900 ions. Calculations for the larger clusters were carried out on a massively parallel computer. A clear ferroelectric transition is observed for clusters with N\ensuremath{\gtrsim}800.