Vibrational states on lithium and sodium surfaces

We present the calculation of vibrational modes, surface energy and lattice relaxation for the (100) and (110) surfaces of lithium and sodium. These values are calculated with the use of interatomic potentials generated within the embedded atom method (EAM). It was found that EAM potentials give an expansion of a few first interlayer spacings. Calculated values of surface energy are in good agreement with available theoretical and experimental data, It is shown that the dependence of the surface energy on the lattice relaxation is extremely small. True and resonance surface states are observed on all surfaces of interest along the symmetry directions and at the symmetry points of the two-dimensional Brillouin zone. It is found that in the case of a (110) surface the phonon frequencies have only a slight dependence on the lattice relaxation. Some more influence is observed for the (100) surface.