Yoshida Norio, Ishizuka Ryosuke, Sato Hirofumi, Hirata Fumio
Department of Theoretical Study, Institute for Molecular Science, Okazaki 444-8585, Japan.
J Phys Chem B. 2006 Apr 27;110(16):8451-8. doi: 10.1021/jp0568834.
The temperature and density dependence of the molecular and thermodynamic properties of water is investigated theoretically by means of the ab initio electronic structure theory combined with the reference interaction site model method, so-called RISM-SCF. We consider the autoionization process (H2O + H2O right harpoon over left harpoon H3O+ + OH-) by regarding H2O, H3O+, and OH- as "solute" molecules in an aqueous solution and evaluate molecular geometry, electronic structure, solvation structure, and the ionic product of water (pKw) of these species as functions of thermodynamic conditions. In our previous paper, we calculated these properties by using essentially the same method in a wide range of density values (0.6-1.4 g/cm3). However, the calculation was limited at rather higher density (>0.6 g/cm3) due to the difficulty of convergence, which is inherent to the hypernetted-chain (HNC) closure. The problem is overcome in this study by employing the Kovalenko-Hirata (KH) closure which hybridizes the HNC and the mean-spherical approximation (MSA). Here, we present the results for the thermodynamic range of densities from 0.025 to 1.0 g/cm3 and for temperatures from 300 to 800 K including the supercritical point.
借助从头算电子结构理论并结合参考相互作用位点模型方法（即所谓的RISM - SCF），从理论上研究了水的分子和热力学性质对温度和密度的依赖性。我们将H₂O、H₃O⁺和OH⁻视为水溶液中的“溶质”分子，考虑了自电离过程（H₂O + H₂O ⇌ H₃O⁺ + OH⁻），并评估了这些物种的分子几何结构、电子结构、溶剂化结构以及水的离子积（pKw）随热力学条件的变化。在我们之前的论文中，我们使用基本相同的方法在较宽的密度值范围（0.6 - 1.4 g/cm³）内计算了这些性质。然而，由于超网链（HNC）封闭所固有的收敛困难，计算在相当高的密度（>0.6 g/cm³）时受到限制。本研究通过采用将HNC与平均球近似（MSA）混合的科瓦连科 - 平田（KH）封闭克服了这一问题。在此，我们给出了密度范围从0.025到1.0 g/cm³以及温度范围从300到800 K（包括超临界点）的热力学范围内的结果。
