Molecular dynamics computer simulation of thin films of LiCl, NaCl, KCl and RbCl possessing (100) crystal–vacuum surfaces

Abstract

Equilibrium and dynamic properties of the (100) crystal–vacuum interfaces of LiCl, NaCl, KCl and RbCl have been investigated by the method of molecular dynamics computer simulation using model interionic potentials and for various temperatures between 298 K and the normal crystal melting points. The use of free laminae models as against a static lattice boundary condition is discussed. In either case at least 10 ionic layers are required in the simulations. Using a simple Born–Mayer–Huggins pair potential there was considerable expansion of the layer separations near the interface and significant buckling occurred for the surface layer of LiCl and of NaCl. The inclusion of polarisation forces using a modified Tosi–Doyama potential in the case of NaCl resulted in a slight contraction of the surface interlayer spacings.