Institut für Thermodynamik, Technische Universität Braunschweig, Hans-Sommer-Str. 5, 38106 Braunschweig, Germany.
J Chem Phys. 2012 Sep 14;137(10):104512. doi: 10.1063/1.4749382.
Molecular dynamics simulations for the shear viscosity and self-diffusion coefficient of pure water were performed to investigate the effect of including intramolecular degrees of freedom in simple point charge (SPC) models over a wide range of state points. Results are reported for the flexible SPC/Fw model, its rigid SPC counterpart, and the widely used SPC/E model. The simulations covered the liquid phase from 277.15 to 363.15 K and the supercritical phase at 673.15 K and pressures up to 200 MPa. The flexibility exhibited by the SPC/Fw model results in slowing down of the dynamics. That is, it results in higher shear viscosities and lower diffusion coefficients than can be obtained from the rigid model, resulting in better agreement with experimental data. Significantly, the SPC/Fw model can be used to adequately predict the diffusion coefficients at ambient and supercritical temperatures over a wide range of pressures.
为了研究在广泛的状态点下包含分子内自由度对简单点电荷（SPC）模型的纯水剪切黏度和自扩散系数的影响，我们对纯水分子进行了分子动力学模拟。报告了柔性 SPC/Fw 模型、其刚性 SPC 对应物以及广泛使用的 SPC/E 模型的结果。模拟涵盖了从 277.15 到 363.15 K 的液相、在 673.15 K 和高达 200 MPa 的压力下的过冷相。SPC/Fw 模型表现出的柔韧性导致动力学减缓。也就是说，它会导致更高的剪切黏度和更低的扩散系数，与实验数据更吻合。值得注意的是，SPC/Fw 模型可以在很宽的压力范围内适当地预测环境温度和超临界温度下的扩散系数。
