Molecular dynamics study of methane in water: diffusion and structure
Molecular dynamics study of methane in water: diffusion and structure
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DOI：
10.1080/08927020601039598
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发表时间：
2006-12
影响因子：
2.1
通讯作者：
J. Zhang;S. Piana;R. Freij-Ayoub;M. Rivero;S. Choi
中科院分区：
文献类型：
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作者：
J. Zhang;S. Piana;R. Freij-Ayoub;M. Rivero;S. Choi
本文给出了恒定NPT体系中水-甲烷混合物在T = 270、300 K和P = 8.104 × 107 Pa条件下的扩散系数和结构的分子动力学模拟结果。我们所研究的体系由1个、4个和8个CH4分子和不同的H2O分子组成，对应的甲烷浓度分别为0.081、0.324和0.643 mol/l。所有模拟中使用的分子间电位均为水[1]的四位点TIP4P模型和CH4-H2O[2]的拟合Lennard-Jones 12-6电位。结果表明，甲烷浓度对水的结构和水分子间氢键的形成影响不大。氢键数、氢键长度和氢键角与温度和密度下甲烷浓度无关。我们还发现氢键的数量和角度对温度很敏感。温度的升高使氢键的数量减少，角度增大。随着温度的降低，水氧-氧径向分布函数的第1峰和第2峰增加，表明水合壳水分子的结构增强。水的自扩散系数对甲烷浓度和温度敏感。
We present molecular dynamics simulation results for the diffusion coefficients and structure of water–methane mixtures in constant NPT ensembles, at T = 270, 300 K and P = 8.104 × 107 Pa. The systems we have studied consist of one, four and eight CH4 molecules and varying H2O molecules per unit cell, which correspond to methane concentration of 0.081, 0.324 and 0.643 mol/l, respectively. The intermolecular potentials used in all the simulations were the four-site TIP4P model of water [1] and the fitted Lennard-Jones 12-6 potential for CH4–H2O [2]. Our results show that the methane concentration has little impact on the structure of water and the formation of hydrogen bonds (H-bonds) between water molecules. The H-bond numbers, H-bond length and the H-bond angle are independent of the methane concentration at the temperatures and densities examined in this study. We also find that the number of H-bonds and angles are sensitive to the temperature. The rise of temperature produces a decrease in the number and an increase in the angle of the H-bonds. Enhanced structuring of the hydration-shell water molecules is indicated by an increase of the first and second peak in the water oxygen–oxygen radial distribution function as temperature is decreased. The self-diffusion coefficient of water is sensitive to the methane concentration and temperature.