Determination of a transferable interatomic potential for alkali-metal perchlorates and its application to morphological modelling

Abstract

The development of an interatomic potential for alkali-metal perchlorates is presented. The potential is fitted to orthorhombic sodium perchlorate and transferred to the perchlorates of caesium, potassium and rubidium. The derived potential data provide a consistent fit to the known crystal structures and elastic constants. Transferability of the potential to the cubic phase of sodium perchlorate leads to a poorer match to experimental data, which perhaps reflects the fact that this phase only stabilises at a high temperature. Unrelaxed and relaxed surface and attachment energies for the low-index crystal planes are calculated for potassium perchlorate, from which crystal morphologies are predicted. The simulations provide a good match to experimental growth morphologies using the Hartman–Perdok attachment energy model, but a poorer one using the more classical Gibbs–Wulff surface-energy model. Potential growth mechanisms, based on these observations, are discussed.