A pseudopotential approach to the electronic structure of dilute transitional and noble metal impurity systems

Abstract

A generalised pseudopotential formalism for calculating the change in electronic structure Delta N(E) of transitional impurity systems has been employed to recast the Green function analysis of Riedinger (1971) for dilute transitional impurity systems into a pseudopotential framework. The required pseudo Green's functions are evaluated from a model Hamiltonian representation of the host metal band structure. For the difference pseudopotential at the impurity site the authors employ a parametrised, optimised model potential which is made partially self-consistent through the application of the Friedel sum rule. This pseudopotential method is then applied to a variety of dilute transitional impurity systems in an endeavour to assess its overall validity. The first systems considered are the dilute noble metal-palladium alloys CuPd, AgPd and AuPd and the resulting Delta N(E) are found to yield Pd virtual bound state (VBS) resonance peaks whose positions and widths are in fairly good agreement with experiment. The method is then applied to the dilute PdAu alloy system and produces a Au VBS resonance near the bottom of the Pd d band as supported by photoemission studies. Finally the authors consider the dilute noble alloys for which the difference in chemical valence of the two components is zero. Calculations for both AgAu and AuAg confirm that there is an effective charge transfer in these systems of around 0.3 e.