Modification of Guest and Saunders open shell SCF equations to exclude BSSE from molecular interaction calculations

The self-consistent field (SCF) for molecular-interactions algorithm, particularly devised to compute intermolecular interactions, is extended to the case in which one of the two interacting fragments is an open shell system. The method excludes the basis set super-position error in an a priori fashion. To preserve the simplicity of the standard SCF procedure, Guest and Saunders equations concerning the open shell fragment are modified at the cost of a negligible complication with respect to the usual algorithm.