Nitrogen overlayer on reconstructed Ni(100): Lattice dynamics and surface-phonon dispersion

Abstract

We present here a lattice-dynamical study of the dispersion of surface phonons and resonances of the c(2×2) overlayer of nitrogen on p4g-reconstructed Ni(100) along the Γ¯–X¯ direction in the two-dimensional Brillouin zone. With the adsorbate atoms sitting in the fourfold hollow site at a distance of 0.2 Å above the Ni surface, the calculations reproduce the main features of the observed dispersion of the surface modes, identify the origin of these modes, and isolate those characteristics which are peculiar to the reconstructed surface. Several features in the phonon dispersion curves are shown to be signatures of surface reconstruction.