A similarity transformation of the schrodinger equation and its application in pseudopotential theory

The Schrodinger equation for stationary states is cast into the form of a new pseudopotential equation by means of a similarity transformation. Using this formalism an analytical expression for Austin, Heine and Sham's general pseudopotential is obtained. The orthogonalization terms appearing in the pseudopotential equation are eliminated, thus reducing it to a pure potential problem which is solved with a combined scheme of matrix algebra and perturbation theory. As an example some results relating to the band structure of bcc lithium calculated by this technique are presented.