MATRIX-ELEMENTS OF THE ELECTRON-PHONON INTERACTION IN THE RIGID ELECTRON-DENSITY DISPLACEMENT APPROXIMATION

We present a method for electron-phonon matrix element calculations ba sed on a rigid displacement of in-sphere electron densities. This meth od may be viewed as an extension of the famous rigid muffin-tin approx imation. At the same time it allows one to take into account tile long -range Coulomb interactions, tile collective character of ion displace ments in phonon modes, and effects due to the anisotropy of electron d ensities inside the muffin-tin spheres. Non-muffin-tin corrections are shown to cause electron-ion scattering selection rule variations.