A MOLECULAR-DYNAMICS STUDY OF A NEARLY INCOMMENSURATE OVERLAYER ON A METAL-SUBSTRATE

We have examined the dynamics of a nearly incommensurate metal overlayer on a metal substrate using the technique of molecular dynamics. We have chosen the parameters in our model of the interatomic forces between atoms to fit the experimentally observed perpendicular vibration frequency of a silver overlayer on Ni(100). The corrugation of the silver-nickel interaction is not known. With this model it is possible to vary the corrugation of the adatom-substrate interaction potential. Thus we can study, in a general way, the effects of corrugation on the phonon spectrum and the dynamics of adatoms. At high temperatures (room temperature and above) we find the metal atoms undergo large displacements with respect to the substrate. The effects of these displacements on the phonon spectra are examined as a function of temperature and the corrugation of the interaction potential. The results will be of use to experimentalists studying the vibrations of nearly incommensurate systems.