Modeling molecular and ionic absolute solvation free energies with quasi-chemical theory bounds - Condensed Matter > Statistical MechanicsReport as inadecuate




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Abstract: A recently developed statistical mechanical Quasi-Chemical Theory QCT hasled to significant insights into solvation phenomena for both hydrophilic andhydrophobic solutes. The QCT exactly partitions solvation free energies intothree components: 1 inner-shell chemical, 2 outer-shell packing, and 3outer-shell long-ranged contributions. In this paper, we discuss efficientmethods for computing each of the three parts of the free energy. A Bayesianestimation approach is developed to compute the inner-shell chemical andouter-shell packing contributions. We derive upper and lower bounds on theouter-shell long-ranged portion of the free energy by expressing this componentin two equivalent ways. Local, high energy contacts between solute and solventare eliminated by spatial conditioning in this free energy piece, leading tonear-Gaussian distributions of solute-solvent interactions energies. Thus, theaverage of the two mean-field bounds yields an accurate and efficient freeenergy estimate. Aqueous solvation free energy results are presented forseveral solutes, including methane, perfluoromethane, water, and the sodium andchloride ions. The results demonstrate the accuracy and efficiency of themethods. The approach should prove useful in computing solvation free energiesin inhomogeneous, restricted environments.



Author: David M. Rogers, Thomas L. Beck

Source: https://arxiv.org/



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