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本文采用分子动力学方法研究了热平衡条件下的汽液界面的动力学行为和热力学性质。统计获得了界面区的密度、压力张量及温度的分布，并且从分子层次观察分析了界面结构和动力学特性。研究表明汽液界面是一个随时间起伏涨落的曲面，界面层的分子并不是处于液相和蒸汽相之间的一种过渡状态，从汽相到液相密度的连续变化是长时间的统计结果，汽液过渡区的厚度与汽液界面区的密度涨落的范围是一致的。对于平衡条件下的汽液界面，由于汽液相变的影响，在紧贴界面处存在一个分子平均动能非平衡分布的区域。此非平衡区域的存在与汽液两相的宏观热平衡并不矛盾，但可能对蒸发/凝结流率的估计有不可忽略的影响。

Dynamic behaviors and thermodynamic properties of liquid-vapor interface atequilibrium are studied with molecular dynamics simulations. The density,the pressure tensor, and the temperature profiles are obtained. Meanwhile,the structure and the dynamic behavior of the interface are analyzed fromthe molecular level. The simulations show that, for the liquid-vapor coexistentsystem, there is a local thermal non-equilibrium area close to the liquidsurface because of the liquid-vapor phase change, while thermal equilibriumcondition is attained outside the interface more than several molecules'diameters. In addition, simulation and experiment show that the liquid-vaporinterface is a wavy surface undulating with time, and the change of the localdensity from the liquid to the vapor is abrupt, the continuous densityprofiles are only statistical results. The thermal non-equilibrium distributionthrough the interface region is caused by the energy transport between theliquid and the vapor phase. For the reason of the small size of the non-uniformtemperature area, the existence of the local non-equilibrium area does notconflict with the macroscopic thermal equilibrium theory. However, the thermalnon-equilibrium distribution may work on the liquid-vapor phase change and haveeffect on the estimation of evaporation/condensation flux.