RELAXATION AND FORCE-CONSTANTS NEAR FCC TRANSITION-METAL SURFACES

Within the tight-binding approximation used together with the moment method, we get a contraction of the surface layer of transition metals. This result is discussed in view of recent experimental measurements. We notably show that this top layer contraction strongly enhances force constants between atoms close to the surface giving rise to a localized step phonon at a frequency above the bulk phonon spectrum. The relaxation energy is also calculated. This term is shown to favour monoatomic steps but in any case it remains quite small. © 1979.