Surface phonons on Pb(111)

Abstract

We present an ab initio study of the lattice dynamics of the Pb(111) surface. Thecalculations were carried out within the density-functional theory using a linear responseapproach in the mixed-basis pseudopotential representation. We observe a rich spectrum ofsurface localized modes, and make a detailed assignment to measured modes in a recenthelium-atom scattering experiment. We find that the inclusion of spin–orbit couplingconsiderably softens the phonon spectrum of the surface, thereby improving the agreementwith experiment significantly.