Semiempirical models for image electrostatics. I. Bare external charge

We develop a simple semiempirical Pariser-Parr-Pople-type model of a metal. It can be used for studies of adsorption and of the interactions between t he metal surface and external charges, and is compatible with ab initio des cription of the molecules outside the metal. We investigate the dependence of the image-type field on the few parameters that control the model behavi or, and develop a simple direct minimization self-consistent field techniqu e that is useful for convergence in nearly degenerate cases. (C) 2001 Ameri can Institute of Physics.