Structure and dynamic stability of a multilayer Na film on the Cu(001) surface

Mechanisms of atomic layer-by-layer formation of the equilibrium structure of multilayer Na film on the Cu(001) surface have been studied taking into account relaxation and dynamic (phonon) processes. It has been shown that the atomic rearrangement of the substrate-commensurate c(2$\times$2) superstructure of the first Na monolayer to a bcc (110)-oriented structure begins with the second monolayer. The dynamic contribution to the formation of the structure of the growing Na film has been estimated. It has been shown that phonon modes select exponentially observed structures from statically favorable structures. All calculations have been performed with interatomic potentials constructed with the embedded atom method. The comparison of the calculated vibrational frequencies with the existing experimental data has demonstrated their good agreement.