Computer simulation of liquids
Computer simulation of liquids
A combined quantum mechanical and molecular mechanical potential for molecular dynamics simulations
Journal of Computational Chemistry
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While most of chemistry occurs in solution, most of computational chemistry is concerned with isolated molecules. The situation is changing rapidly, however. A host of new algorithms have appeared for treating the quantum-mechanical electronic structure of molecules surrounded by solvent. The difficulty of the problem is brought home by considering that the brute-force approach--that is, treating the whole system of solute and solvent as one large isolated molecule via the conventional techniques of computational quantum mechanics--isn't even practical enough to contend with and then lose out to the new approaches. The conventional technique would be too difficult to even be slow; it is untried with a system of this size and almost unthinkable. The most successful of the new approaches are based on treating a subsystem (the solute) with full quantum mechanics and the rest (the solvent) via some shortcut.Gao and Furlani survey one of the most promising of such approaches, in which the solvent, for example, water, is treated by molecular mechanics. This means that the solvent molecules interact with one another and with the solute through classical mechanics and classical electrostatics. Since solvent molecules are not actually classical entities, this involves modeling, and modeling involves parameters. The authors show that the parameters obtained for purely quantal and purely classical models can be used in this new combination for modeling organic chemical and biochemical processes in solution. The method takes advantage of both the accuracy offered in quantum-mechanical calculations and the efficiency provided by classical force fields. The authors describe the method and provide examples of applying it to chemical reactions, photochemical processes, and electron transfer in solution. For some of the applications the method competes in accuracy and ease of use with experimental work.The authors may be reached at the Department of Chemistry, State University of New York at Buffalo, Buffalo, NY 14260-3000, e-mail jiali@tams.chem.buffalo.edu or furlani@blizzard.chem.buffalo.edu.