Basic ideas for the correction of semiempirical methods describing H-bonded systems

In this Letter, we show how semiempirical methods may be improved to descri be hydrogen-bonded systems and proton transfer reactions. The approach cons ists in a redefinition of the core-core interaction terms that, as previous ly shown, are at the origin of spurious artifacts in standard methods. The parameterization of the new core-core functions is done using ab initio dat a of the intermolecular potential energy surfaces (PESs), which permits rea ching the correct behavior at short and long interatomic distances. Here we report the parameters for O-O, O-H and H-H interactions. Extension to othe r atom pairs seems feasible, so the development of a semiempirical method a dapted to the study of intermolecular interactions might be envisaged. (C) 2000 Elsevier Science B.V. All rights reserved.