Electronic States as Linear Combinations of Muffin-Tin Orbitals

Abstract

A general method for the calculation of electronic states in solids and molecules is proposed. As in the augmented-plane-wave scheme, we use the variational principle for the Hamiltonian in an energy-dependent basis. The basis functions, so-called muffin-tin orbitals, are generalizations of Heine's resonant orbitals. For a muffin-tin potential, the secular matrix has form $(1+\ensuremath{\Lambda}U)\ensuremath{\Lambda}$, where $\ensuremath{\Lambda}$ is the matrix of the Korringa-Kohn-Rostoker (KKR) method and $U$ is a simple matrix element of the potential. In contrast to the KKr scheme, the present method easily includes perturbations to the muffin-tin Hamiltonian.