Department of Chemistry and Supercomputer Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, USA.
Acc Chem Res. 2008 Jun;41(6):760-8. doi: 10.1021/ar800019z.
Continuum mean-field models that have been carefully designed to address the various electrostatic and nonelectrostatic interactions that develop between a molecule and a surrounding medium are particularly efficient tools for studying the effects of condensed phases on molecular structure, energetics, properties, spectra, interaction potentials, and dynamics. The SM8 model may be combined with density functional theory or Hartree-Fock theory to describe a solute's electronic structure and its self-consistent-field polarization by a solvent. A key feature is the use of class IV charge models to obtain accurate charge distributions (either in the vapor phase or in solution), even when using small basis sets that are affordable for large systems. A second key feature is that nonelectrostatic effects due to cavity formation, dispersion interactions, and changes in solvent structure are included in terms of empirical atomic surface tensions that depend on geometry but do not require atom-type assignments by the user. Use of an analytic surface area algorithm provides very stable energy gradients that allow geometry optimization in solution. The SM8 continuum model, the culmination of a series of SMx models (x = 1-8), permits the modeling of such diverse media as aqueous and organic solvents, soils, lipid bilayers, and air-water interfaces. In addition to predicting accurate transfer free energies between gaseous and condensed phases or between two different condensed phases, SMx models have been useful for predicting the significant influence of condensed phases on processes associated with a change in molecular charge, including acid/base equilibria and oxidation/reduction processes. In this Account, we provide an overview of the algorithms associated with the computation of free energies of solvation in the SM8 model. We also compare the accuracies of the SM8 model with those of other continuum solvation models. Finally, we highlight applications of the SM8 models to compute ionic solvation free energies, oxidation and reduction potentials, and pK(a) values.
精心设计的连续介质平均场模型，旨在解决分子与周围介质之间产生的各种静电和非静电相互作用，是研究凝聚相对分子结构、能量、性质、光谱、相互作用势和动力学影响的特别有效工具。SM8 模型可与密度泛函理论或 Hartree-Fock 理论结合使用，以描述溶质的电子结构及其在溶剂中的自洽场极化。一个关键特点是使用第四类电荷模型来获得准确的电荷分布（无论是在气相还是在溶液中），即使使用对于大型系统来说负担得起的小基组。第二个关键特点是，空腔形成、色散相互作用和溶剂结构变化引起的非静电效应，以依赖于几何形状但不需要用户进行原子类型分配的经验原子表面张力项来表示。使用解析表面积算法可提供非常稳定的能量梯度，允许在溶液中进行几何优化。SM8 连续介质模型是一系列 SMx 模型（x = 1-8）的结晶，允许对多种介质进行建模，如水溶液和有机溶剂、土壤、脂质双层和空气-水界面。除了预测气相和凝聚相之间或两种不同凝聚相之间准确的转移自由能外，SMx 模型还可用于预测凝聚相对与分子电荷变化相关的过程的显著影响，包括酸碱平衡和氧化还原过程。在本报告中，我们提供了 SM8 模型中溶剂化自由能计算相关算法的概述。我们还比较了 SM8 模型与其他连续溶剂化模型的准确性。最后，我们强调了 SM8 模型在计算离子溶剂化自由能、氧化还原电位和 pK(a)值方面的应用。
