Electronic response to surface atomic displacements on Mo (001)

Abstract

The electronic contribution to the energy of surface phonons is decomposed into a wavevector-dependent term which depends only on the response function in the surface region, plus a wavevector-independent term giving the energy change due to a uniform surface displacement. The wavevector-dependent term is evaluated for the unreconstructed Mo (001) surface, using the matching Green function method to calculate the electronic response function, and the rigid muffin-tin approximation to determine the electron-phonon matrix elements. It is found that the large density of the surface states at the Fermi energy, and the states bonding the surface atoms to the bulk, favour lateral displacements, through the wavevector of the corresponding surface phonon anomaly disagrees with the experimentally observed reconstruction. Periodic vertical displacements of the surface atoms are energetically unfavourable.