Molecular dynamics study of kinetic boundary condition at an interface between argon vapor and its condensed phase
Molecular dynamics study of kinetic boundary condition at an interface between argon vapor and its condensed phase
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DOI：
10.1063/1.1763936
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发表时间：
2004-08-01
影响因子：
4.6
通讯作者：
Fujikawa, S
中科院分区：
文献类型：
--
作者：
Ishiyama, T;Yano, T;Fujikawa, S
考虑了蒸汽与冷凝相界面上的蒸发和冷凝。采用氩气分子动力学数值方法，对玻尔兹曼方程动力学边界条件的有效性进行了研究。玻尔兹曼方程规定了分子从界面流出的速度分布函数。通过对真空蒸发过程的模拟，发现了由冷凝相温度决定的自然蒸发通量。然后可以确定平衡状态下的冷凝系数，而不会有任何歧义。发现在三点温度以下凝结系数接近于1，并随着温度的升高而逐渐减小。在低温下，自发蒸发分子的速度分布几乎是麦克斯韦的一半。这一事实支持了目前广泛使用的动力学边界条件。另一方面，在高温下，速度分布偏离了半麦克斯韦公式。(C) 2004年美国物理研究所。
The evaporation and condensation at an interface of vapor and its condensed phase is considered. The validity of kinetic boundary condition for the Boltzmann equation, which prescribes the velocity distribution function of molecules outgoing from the interface, is investigated by the numerical method of molecular dynamics for argon. From the simulations of evaporation into vacuum, the spontaneous-evaporation flux determined by the temperature of condensed phase is discovered. Condensation coefficient in equilibrium states can then be determined without any ambiguity. It is found that the condensation coefficient is close to unity below the triple-point temperature and decreases gradually as the temperature rises. The velocity distribution of spontaneously evaporating molecules is found to be nearly a half-Maxwellian at a low temperature. This fact supports the kinetic boundary condition widely used so far. At high temperatures, on the other hand, the velocity distribution deviates from the half-Maxwellian. (C) 2004 American Institute of Physics.