An estimate of the effect of lattice relaxation on deviations from Matthiessen's rule in potassium

The relaxation of host potassium ions about a sodium impurity is computed using the method of lattice statics. The anisotropy in the relaxation produces anisotropy in the computed residual scattering times which in turn produce deviations from Matthiessen's rule. The computed values for the deviation are significant at temperatures above about 15K, where anisotropy due to electron-phonon scattering becomes small.