Molecular Dynamics Analysis on Gas-Surface Interaction

用分子动力学方法模拟和分析了气体分子在洁净完整表面上的散射过程。首先，使用864个Lennard-Jones型分子计算薄固体膜的热平衡状态，然后改变势参数和质量的气体分子碰撞到该表面上。对于一个参数的情况下，数百个散射进行了模拟。在某些情况下，气固相互作用势采用莫尔斯型势。数值结果如下：1.气体分子的散射行为不同于扩散模型或麦克斯韦模型.气体分子的粘附概率主要受气体初始速度和势阱深度的影响.非粘性分子的平均法向动量与其初始法向动量有很好的相关性.利用Xe-Pt（111）体系的莫尔斯势，计算出的粘附几率与Tully等人的实验结果一致。气体向表面的能量传递是有限的，在一定的时间内，即气体分子在一次碰撞中动能的两个最大值之间。一次碰撞的能量转移量与第一极大动能密切相关，其分布函数受气体分子切向动量的控制。

The scattering process of a gas molecule on a clean and complete surface is simulated and analyzed by the molecular dynamics method. First, a thermal equilibrium state of a thin solid film is calculated using 864 molecules of Lennard-Jones type, and then the gas molecule, whose potential parameters and its mass is changed, has collide on to this surface. For one case of parameters hundreds of scattering is simulated. In some cases the Morse type potential is used for gas-solid interaction potential. The numerical results are :1. The scattering behavior of gas molecule is differ from that in the diffuse model or Maxwell model.2. The sticking probability of gas molecule is affected mainly by the initial gas velocity and the potential well depth.3. The average of normal momentum of non-sticking molecules is very correlated with the initial normal momentum of them.4. Using the Morse potential for the Xe-Pt (111) system, the sticking probability is agree with the experiment of Tully et al.5. The energy transfer of gas to surface is limited in a certain period, that between the two maximum of kinetic energy of gas molecule in one collision. The amount of this energy transfer for one collision is very correlated to the kinetic energy at first maximum and its distribution function is controlled by the tangential momentum of gas molecule.