Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
J Chem Phys. 2011 Apr 14;134(14):144702. doi: 10.1063/1.3579480.
Molecular dynamics simulations have been performed to examine the thermodynamic properties of methane/water interface using two different water models, the TIP4P/2005 and SPC/E, and two sets of combining rules. The density profiles, interfacial tensions, surface excesses, surface pressures, and coexisting densities are calculated over a wide range of pressure conditions. The TIP4P/2005 water model was used, with an optimized combining rule between water and methane fit to the solubility, to provide good predictions of interfacial properties. The use of the infinite dilution approximation to calculate the surface excesses from the interfacial tensions is examined comparing the surface pressures obtained by different approaches. It is shown that both the change of methane solubilities in pressure and position of maximum methane density profile at the interface are independent of pressure up to about 2 MPa. We have also calculated the adsorption enthalpies and entropies to describe the temperature dependency of the adsorption.
采用两种不同的水分子模型（TIP4P/2005 和 SPC/E）和两组组合规则，通过分子动力学模拟研究了甲烷/水界面的热力学性质。在较宽的压力条件范围内计算了密度分布、界面张力、表面过剩量、表面压力和共存密度。使用 TIP4P/2005 水分子模型，通过与溶解度拟合的优化组合规则来拟合水和甲烷之间的相互作用，从而对界面性质进行了很好的预测。通过比较不同方法得到的表面压力，考察了从界面张力计算表面过剩量时使用无限稀释近似的合理性。结果表明，甲烷在压力下的溶解度变化以及界面处甲烷最大密度分布的位置在约 2 MPa 以下时与压力无关。我们还计算了吸附焓和熵来描述吸附的温度依赖性。
