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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Computational studies of liquid water and diluted water in carbon tetrachloride
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Computational studies of liquid water and diluted water in carbon tetrachloride

机译：四氯化碳中液态水和稀释水的计算研究

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Molecular dynamics simulations were carried out to study solvent effects on the energetic and dynamical properties of water molecules in liquid water and in carbon tetrachloride (CCl4). In these studies, the free-energy profiles or potentials of mean force (PMF) for water dimers in both solvents were computed. The computed PMF results showed a stable minimum near 3 angstrom for the O-O separation, with a minimum free energy of about -2.8 kcal/mol in CCl4, as compared to a value of -0.5 kcal/mol in liquid water. The difference in free energy in water as compared to that in CCl4 was expected and is the result of competition from surrounding water molecules that are capable of forming hydrogen bonds in the liquid water. This capability is absent in the diluted water found in CCl4. We found that the rotational motions of H2O/D2O were nonisotropic, with the out-of-plane vector correlation times in H2O/D2O varying from 5.6/5.8 ps at 250 K to 0.57/0.56 ps at 350 K and the corresponding OH/OD bond vectors varying from 6.5/7.7 ps to 0.75/0.75 ps. The results compare reasonably well to the available NMR experimental and computer simulation data on the same system (Farrar; Skinner; et al. J. Am. Chem. Soc. 2001, 123, 8047). For diluted water in CCl4, we found the computed rotational correlation times also were nonisotropic and much longer than the corresponding NMR experimental values at the same concentration (Farrar; et al. J. Phys. Chem. A 2007, 111, 6146). Upon analyzing the water hydrogen-bonding patterns as a function of water concentration, we conclude that the differences in the rotational correlation times mainly result from the formation of water hydrogen-bonding networks as the water concentration is increased in liquid CCl4. In addition, we found the rotational correlation times to be substantially faster in liquid CCl4 than in liquid water.
机译：进行了分子动力学模拟，以研究溶剂对液态水和四氯化碳（CCl4）中水分子的能量和动力学性质的影响。在这些研究中，计算了两种溶剂中水二聚体的自由能曲线或平均力势（PMF）。计算出的PMF结果显示，O-O分离的最小值稳定在3埃附近，而在CCl4中的最小自由能约为-2.8 kcal / mol，而液态水的最小值为-0.5 kcal / mol。与CCl4相比，水中的自由能有所不同，这是与周围水分子竞争的结果，这些水分子能够在液态水中形成氢键。 CCl4中发现的稀释水不具备此功能。我们发现H2O / D2O的旋转运动是各向同性的，H2O / D2O中的平面外矢量相关时间从250 K时的5.6 / 5.8 ps到350 K时的0.57 / 0.56 ps以及相应的OH / OD键向量从6.5 / 7.7 ps到0.75 / 0.75 ps不等。结果与在相同系统上可获得的NMR实验和计算机模拟数据相当合理地比较（Farrar; Skinner;等人，J。Am。Chem。Soc。2001，123，8047）。对于CCl4中的稀释水，我们发现，在相同浓度下，计算出的旋转相关时间也各向同性，并且比相应的NMR实验值长得多（Farrar;等人，J。Phys。Chem。A 2007，111，6146）。通过分析水氢键模式作为水浓度的函数，我们得出结论，随着液体CCl4中水浓度的增加，旋转相关时间的差异主要是由于水氢键网络的形成所致。此外，我们发现液体CCl4中的旋转相关时间比液体水中的旋转相关时间快得多。

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