离子水合自由能的从头算分子动力学计算
Ab initio molecular dynamics calculations of ion hydration free energies
摘要：
我们应用从头算分子动力学（AIMD）方法结合热力学积分或“量子路径”技术来计算Li+，Cl-和Ag+离子的固有水合自由能。使用Perdew-Burke-Ernzerhof泛函，为经典力场应用开发的自适应方法，并对表面势（phi）贡献进行一致假设，我们获得了绝对AIMD水合自由能（Δ G（hyd））在Tissandier的几千卡/摩尔内，或优于4%[J. Phys. Chem. A 102，7787（1998）]的实验值与SPC/E水模型预测增加。不受表面电位影响的Li+/Cl-和Ag+/Cl- AIMD Δ G（hyd）之和分别在实验值的2.6%和1.2%范围内。我们还报道了在水中过渡金属离子Ag++Ni+-> Ag+ Ni ~（2+）氧化还原反应的自由能变化。该反应的预测表明，现有的估计三角洲G（hyd）的不稳定的辐解中间体，如镍+可能需要进行广泛的修订。
英文摘要：
We apply ab initio molecular dynamics (AIMD) methods in conjunction with the thermodynamic integration or "lambda-path" technique to compute the intrinsic hydration free energies of Li+, Cl-, and Ag+ ions. Using the Perdew-Burke-Ernzerhof functional, adapting methods developed for classical force field applications, and with consistent assumptions about surface potential (phi) contributions, we obtain absolute AIMD hydration free energies (Delta G(hyd)) within a few kcal/mol, or better than 4%, of Tissandier 's [J. Phys. Chem. A 102, 7787 (1998)] experimental values augmented with the SPC/E water model phi predictions. The sums of Li+/Cl- and Ag+/Cl- AIMD Delta G(hyd), which are not affected by surface potentials, are within 2.6% and 1.2 % of experimental values, respectively. We also report the free energy changes associated with the transition metal ion redox reaction Ag++Ni+-> Ag+Ni2+ in water. The predictions for this reaction suggest that existing estimates of Delta G(hyd) for unstable radiolysis intermediates such as Ni+ may need to be extensively revised.
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