No abstract

A simplified tight-binding description of the electronic structure is often necessary for complex studies of surfaces of transition metal compounds. This requires a self-consistent parametrization of the charge redistribution, which is not obvious for late transition series elements (such as P d, Cu, Au), for which not only d but also s − p electrons have to be taken into account. We show here, with the help of ab initio FP-LMTO approach, that for these elements the electronic charge is unchanged from bulk to the surface, not only per site but also per orbital. This implies different level shifts for each orbital in order to achieve this orbital neutrality rule. Our results invalidate any neutrality rule which would allow charge redistribution between orbitals to ensure a common rigid shift for all of them. Moreover, in the case of P d, the power law which governs the variation of band energy with respect to coordination number, is found to differ significantly from the usual tight-binding square root. * The CRMC2 is also associated to the Universities of Aix-Marseille II and III.

No abstract

Using the ab initio full-potential linear muffin-tin orbital approach we have studied the characteristics of Ge adsorption on three different Ag surfaces. We have analyzed the surface-orientation-dependent characteristics of the Ge adsorption, focusing our attention on comparison between adatom and substitutional adsorption. We find that whereas on the ͑111͒ surface substitutional adsorption is preferential, on the ͑100͒ and ͑110͒ ones the two adsorption modes have similar energetics. Analysis of the adsorption-induced modifications of the electronic structure of both the substrate and the adsorbate supports the thesis that at small coverage, Ge deposition on the Ag surfaces is to a large extent determined by laws characteristic for metal on metal adsorption.