Proposal and numerical test of a simple diabatization scheme

The theory of constructing diabatic electronic wave functions for strongly coupled potential energy surfaces is briefly reviewed. The use of a particu larly simple diabatization scheme is advocated which removes only the leadi ng terms of the nonadiabatic, or derivative, coupling elements. It is teste d numerically for a well-established E X e Jahn-Teller problem and shown to lead to very good (often excellent) agreement with the exact results. (C) 1999 American Institute of Physics. [S0021-9606(99)02719-1].