Modeling molecular and ionic absolute solvation free energies with quasichemical theory bounds

Research output: Contribution to journalArticlepeer-review

30 Scopus citations

Abstract

A recently developed statistical mechanical quasichemical theory (QCT) has led to significant insights into solvation phenomena for both hydrophilic and hydrophobic solutes. The QCT exactly partitions solvation free energies into three components: (1) Inner-shell chemical, (2) outer-shell packing, and (3) outer-shell long-ranged contributions. In this paper, we discuss efficient methods for computing each of the three parts of the free energy. A Bayesian estimation approach is developed to compute the inner-shell chemical and outer-shell packing contributions. We derive upper and lower bounds on the outer-shell long-ranged portion of the free energy by expressing this component in two equivalent ways. Local, high-energy contacts between the solute and solvent are eliminated by spatial conditioning in this free energy piece, leading to near-Gaussian distributions of solute-solvent interaction energies. Thus, the average of the two mean-field bounds yields an accurate and efficient free energy estimate. Aqueous solvation free energy results are presented for several solutes, including methane, perfluoromethane, water, and sodium and chloride ions. The results demonstrate the accuracy and efficiency of the methods. The approach should prove useful in computing solvation free energies in inhomogeneous, restricted environments.

Original languageEnglish
Article number134505
JournalJournal of Chemical Physics
Volume129
Issue number13
DOIs
StatePublished - 2008
Externally publishedYes

Funding

We would like to gratefully acknowledge the support of the NSF (CHE-0709560), the Army MURI program (DAAD19-02-1-0227), and the DOE Computational Science Graduate Fellowship (DE-FG02-97ER25308) for the support of this work. We acknowledge the Ohio Supercomputer Center for a grant of supercomputer time. We especially thank Lawrence Pratt for many helpful discussions.

Fingerprint

Dive into the research topics of 'Modeling molecular and ionic absolute solvation free energies with quasichemical theory bounds'. Together they form a unique fingerprint.

Cite this