A comparative analysis of the vibrational and structural properties of nearly incommensurate overlayer systems

摘要

Using molecular dynamics simulations based on embedded atom method potentials, we have investigated the vibrational properties of the following three systems of nearly hexagonal noble metal monolayers adsorbed on substrates of square symmetry: Ag on Cu(001), Ag on Ni(001) and Au on Ni(001). The corresponding local phonon density of states, mean square amplitudes, and substrate interlayer relaxation of the above systems are compared to identify similarities and differences. A key finding is that the Ag monolayers have a stronger influence on both phonon spectra and vibrational amplitudes of the topmost layer of the Cu(001) surface than that of the nickel substrates. Furthermore, the vibrational amplitudes of the overlayer atoms are shown to be anisotropic and dominant along the incommensurate direction for the three systems. Temperature effects on the vibrational and structural properties are also discussed.