A QM/MM/continuum model for computations in solution: Comparison with QM/MM molecular dynamics simulations

We propose a model for fast quantum mechanical computations of molecules an d processes in solution. The chemical system is described quantum mechanica lly (QM) using density functional theory A few discrete solvent molecules a re described using molecular mechanics (MM) force fields. The bulk solvent is described through a dielectric continuum model. The interaction between the QM/MM aggregate and the continuum is computed by using a multipole mome nt development of the charge distribution of the former. This is an interme diate model between the standard continuum approach and the combined quantu m mechanics and molecular mechanics (QM/MM) technique, in which a large num ber of MM solvent molecules is considered and a statistical simulation of t he solution is performed. The method may also be used to estimate long-rang e interactions in combined QM/MM Monte Carlo or molecular dynamics simulati ons. (C) 2001 John Wiley & Sons, Inc.