DETERMINATION OF A TRANSFERABLE INTERATOMIC POTENTIAL FOR ALKALI-METAL PERCHLORATES AND ITS APPLICATION TO MORPHOLOGICAL MODELING

The development of an interatomic potential for alkali-metal perchlora tes is presented. The potential is fitted to orthorhombic sodium perch lorate and transferred to the perchlorates of caesium, potassium and r ubidium. The derived potential data provide a consistent fit to the kn own crystal structures and elastic constants. Transferability of the p otential to the cubic phase of sodium perchlorate leads to a poorer ma tch to experimental data, which perhaps reflects the fact that this ph ase only stabilises at a high temperature. Unrelaxed and relaxed surfa ce and attachment energies for the low-index crystal planes are calcul ated for potassium perchlorate, from which crystal morphologies are pr edicted. The simulations provide a good match to experimental growth m orphologies using the Hartman-Perdok attachment energy model, but a po orer one using the more classical Gibbs-Wulff surface-energy model. Po tential growth mechanisms, based on these observations, are discussed.