Anisotropic relaxation times for impurity scattering on the Fermi surface

A theoretical calculation is described for the anisotropic relaxation time due to impurity scattering on the Fermi surface of simple metals. The calculation is based on a multiple plane wave scattering formalism using pseudopotentials and phase shifts. The pseudowavefunctions and the Fermi surface are obtained from a four orthogonalised plane wave calculation while the scattering pseudopotentials are taken from form factors which are locally rescreened and corrected for lattice distortion around impurities. Detailed results are presented for impurity in Al. Calculated Dingle temperatures are in reasonable agreement with experimental results. A phase shift model is introduced which allows the Dingle temperature to be expressed in terms of impurity phase shifts and pseudowavefunction amplitudes. These amplitudes have been calculated for several orbits on the Fermi surfaces of Al, In and Pb. The influence of impurities on the low field Hall effect is also discussed.