Chang Tsun-Mei, Dang Liem X
Department of Chemistry, University of Wisconsin-Parkside, 900 Wood Road, Box 2000, Kenosha, WI 53141-2000, USA.
J Phys Chem B. 2005 Mar 31;109(12):5759-65. doi: 10.1021/jp045649v.
Molecular dynamics simulations were carried out to investigate the structural and thermodynamic properties and variations in the dipole moments of the liquid-vapor interfaces of methanol-water mixtures. Various methanol-water compositions were simulated at room temperature. We found that methanol tends to concentrate at the interface, and the computed surface tension shows a composition dependence that is consistent with experimental measurements. The methanol molecule shows preferred orientation near the interface with the methyl group pointing into the vapor phase. The methanol in the mixture is found to have larger dipole moments than that of pure liquid methanol. The strong local field induced by the surrounding water molecules is partly the reason for this difference. The dependence of hydrogen-bonding patterns between methanol and water on the interface and the composition of the mixture is also discussed in the paper.
进行了分子动力学模拟，以研究甲醇 - 水混合物液 - 气界面的结构、热力学性质以及偶极矩的变化。在室温下模拟了各种甲醇 - 水组成。我们发现甲醇倾向于在界面处聚集，计算得到的表面张力呈现出与实验测量结果一致的组成依赖性。甲醇分子在界面附近呈现出优先取向，甲基指向气相。发现混合物中的甲醇比纯液态甲醇具有更大的偶极矩。周围水分子诱导的强局部场是造成这种差异的部分原因。本文还讨论了甲醇与水之间氢键模式对界面和混合物组成的依赖性。
