Quantum Monte Carlo algorithm reactions

Chemical studies usually deal with a solute which can be a single molecule or a molecular complex or transition state in a chemical reaction. In such systems, the role of the solvent is mainly a physical perturbation which can be simulated at a lower theoretical level than that required for the study of the subsystem of chemical interest. The success of continuum models confirms this statement. In order to describe the solution at the molecular level and to perform full statistical mechanics computations on a model of macroscopic sample, one may set up some computationally efficient approaches by limiting the quantum chemical study to the solute and using one of the usual classical force-fields to represent the solvent molecules. The computation of the statistical averages can be done by means of either Monte Carlo or molecular dynamics algorithms. The so-called QM/MM models are now widely used in such chemical studies. 

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