Ond-Resonant Levels in Heavy Alkali Metals

An electron-ion scattering amplitude that takes into account the effects due to the $d$ excited bands in heavy alkali metals is proposed. The $d$ bands are treated as resonant levels, and the scattering amplitude is constructed via an effective-range approximation. The cross section is given in terms of two resonance parameters and of the Born approximation for the pseudopotential. We use a modified form of the nonlocal and energy-dependent Heine-Abarenkov model potential, where the high-angular-momentum components of the potential are properly treated. We test our model by calculating the resistivity and thermoelectric power for the solid phase of K, Rb, Cs. The results give satisfactory agreement with experiment. In particular, for $K$ we find that the strong $d$ nonlocality obtained by Lee and Falicov is equivalent to a $d$ resonance built into the electron-ion scattering amplitude.