A double expansion method for calculating molecular properties

Abstract

Using a form of double perturbation theory we present results of calculations on the ground state energies for the diatomic systems H2 +, HHe2+, H2 and HHe+. For the homonuclear systems the energy values are unexpectedly good. For the heteronuclear cases the results are very encouraging and lead to optimism about the application of the method to larger systems which contain one heavy atom.