Pseudopotential Theory for Atoms and Molecules

Abstract

Abstract An exact pseudopotential theory is presented for atoms and molecules with arbitrary number of valence and core electrons and arbitrary number of nuclei. Using the variation method an equation is derived for the best many-valence-electron wave function which is orthogonalized to the core orbitals. Using this equation the exact equation is derived for the many-valence-electron pseudo-wavefunction which does not have to satisfy any orthogonality conditions. The Hamiltonian of the pseudopotential equation is of surprisingly simple structure and does not depend on the energy and/or on the wave function of the valence electrons. It is shown that the simple model Hamiltonian which is used in many pseudopotential calculations can be derived from the exact equation by two plausible approximations. The theory is elucidated on the example of atoms with two valence electrons.