ENERGY AND ENERGY DERIVATIVES FOR MOLECULAR SOLUTES - PERSPECTIVES OF APPLICATION TO HYBRID QUANTUM AND MOLECULAR METHODS

摘要

We examine the state of the art of the solvation procedure called the polarizable continuum model (PCM), focusing our attention on the basic properties: energy of the solute, solvation energy, and their derivatives with respect to nuclear coordinates. The PCM method is based on the use of an effective solute Hamiltonian, where the solute-solvent potential is described in terms of continuous response functions with boundary conditions given in terms of the solute cavity surface. This exposition is mainly based on recent progress, a large part of which is still in press. The new procedures are quite effective, at the ab initio quantum mechanical level, but cannot be applied to very large solutes for the limitations of computer hardware. We introduce then other methods, presented here for the first time, which make possible the classical calculation of the solvation energy also for very large solutes (a few thousand atoms). The strategy outlined here regards a new method to define cavity surfaces (supplemented with analytical definitions of its partition in tesserae) and of their derivatives, combined with a fast noniterative method to compute solvation energy. Finally, we discuss the introduction of this procedure in hybrid quantum mechanical/molecular mechanics descriptions of large solutes (enzymes), where the quantum description is limited to the reacting portion of the enzyme. (C) 1996 John Wiley & Sons, Inc. [References: 36]