疏水性微孔中水的结构和扩散性质的分子模拟

Structural and Diffusion Properties of Water in Hydrophobic Micropores by Molecular Simulation

用分子动力学(MD)方法模拟了受限在疏水性微孔中的水的结构与动力学行为．分别考察了孔径、温度和压力对水在孔道方向的密度分布和自扩散系数的影响，计算了不同温度下水的径向分布函数，发现在小孔径的微孔中，随着温度的降低，水分子沿孔道的分布逐渐变得不均匀，最终导致气-液相分离，微孔孔道内有明显的分段现象，受限在小孔径微孔中水的自扩散系数大约为体相流体水的20%～30%，并且随着孔径的减小，自扩散系数也减小，同时还发现沿孔道方向的自扩散系数分量大约为孔径方向的4～5倍．提出了微孔中水自扩散系数的关联模型．

The structural and diffusion properties of water confined in hydrophobic micropores were studied by means of molecular dynamics (MD) simulations. The effects of pore width, temperature, and pressure on density distribution in the channel direction and on self-diffusion coefficient were investigated and analyzed, and the radial distribution functions of water in micropores at different temperatures were calculated. In small-size micropores, the distribution of water molecules along the channel direction becomes very inhomogeneous as the temperature decreases, which leads to gas-liquid phase separation. The diffusivity in the direction parrallel with the channel is generally 4 similar to 5 times larger than those in the direction perpendicular to the channel. Finally, a model was proposed to describe the diffusivity of water in micropores as a function of temperature and density.