Molecular dynamics computer simulation of surface properties of crystalline potassium chloride

Abstract

Computer simulation of the (100) face of crystalline potassium chloride has been achieved using the method of molecular dynamics and a lamina model of thickness 10 ionic layers. The basic cell contained 360 ions, interacting via a Tosi–Fumi potential. A solution has been obtained for the long range correction to the Coulomb potential for an ionic lamina. This differs significantly from the solution for a 3-dimensional lattice. Surface distortion, surface energy and stress have been evaluated and agree well with experiment and previous model calculations. The ratios of surface mean square amplitudes of vibration perpendicular to the surface divided by the bulk values show an approximately 25 % anharmonic enhancement over previous calculations. The layerwise velocity autocorrelation functions yield power spectra featuring a peak for the surface mono-layer at 75 cm^–1 which compares favourably with the frequency of surface acoustic modes predicted by previous calculations.