Molecular density functional theory of solvation: from polar solvents to water.
Molecular density functional theory of solvation: from polar solvents to water.
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DOI：
10.1063/1.3589142
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发表时间：
2011-05
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影响因子：
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通讯作者：
Shuangliang Zhao;R. Ramírez;R. Vuilleumier;D. Borgis
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作者：
Shuangliang Zhao;R. Ramírez;R. Vuilleumier;D. Borgis
提出了分子溶剂中溶剂化反应的经典密度泛函理论方法。任意溶质在给定溶剂中的溶剂化性质，都由分子力场描述，可以通过最小化位置和取向相关的自由能密度泛函来获得。在均匀参考流体近似中，仅限于两体关联，泛函的未知多余项近似为纯溶剂的角度依赖的直接关联函数。我们表明，这个功能可以提取从一个初步的MD模拟的纯溶剂通过计算的角度依赖的对分布函数，并随后求解分子Ornstein-Zernike方程使用离散的角度表示。相应的功能，然后可以最小化在一个三维立方网格的位置和高斯-勒让德角网格的取向，以提供溶剂化结构和自由能的任意溶质的存在下。这两步程序被证明是更有效的比直接分子动力学模拟结合热力学积分方案。该方法被证明是相关的和准确的原型极性溶剂，如Stockmayer溶剂或乙腈。对于水，虽然对中性或中等电荷溶质是正确的，但它往往低估了氢键溶质（如球形离子）周围的四面体溶剂化结构。这可以通过引入合适的三体相关项来校正，从而恢复准确的水合结构和令人满意的能量学。
A classical density functional theory approach to solvation in molecular solvent is presented. The solvation properties of an arbitrary solute in a given solvent, both described by a molecular force field, can be obtained by minimization of a position and orientation-dependent free-energy density functional. In the homogeneous reference fluid approximation, limited to two-body correlations, the unknown excess term of the functional approximated by the angular-dependent direct correlation function of the pure solvent. We show that this function can be extracted from a preliminary MD simulation of the pure solvent by computing the angular-dependent pair distribution function and solving subsequently the molecular Ornstein-Zernike equation using a discrete angular representation. The corresponding functional can then be minimized in the presence of an arbitrary solute on a three-dimensional cubic grid for positions and Gauss-Legendre angular grid for orientations to provide the solvation structure and free-energy. This two-step procedure is proved to be much more efficient than direct molecular dynamics simulations combined to thermodynamic integration schemes. The approach is shown to be relevant and accurate for prototype polar solvents such as the Stockmayer solvent or acetonitrile. For water, although correct for neutral or moderately charged solute, it tends to underestimate the tetrahedral solvation structure around H-bonded solutes, such as spherical ions. This can be corrected by introducing suitable three-body correlation terms that restore both an accurate hydration structure and a satisfactory energetics.