双甘氨肽与高定向热解石墨的散射动力学研究

本文通过反应力场来研究中性双甘氨肽与高取向热解石墨的碰撞动力学过程，分别模拟初始入射角度为0o、20o、45o和70o以及入射能量为481.5 kJ/mol和表面温度为677 K的情况，并且确定和分析了散射产物的角度分布、平动能分布、内能分布和表面滞留时间分布. 双甘氨肽是一种多原子分子，具有较多的低频振动模式和较强的表面吸附相互作用，这些使得碰撞过程的表面滞留时间较长和容易造成能量损失，尤其是表面法线方向. 由于碰撞分子的动量沿表面法线方向上明显地发生损失，而沿表面平行方向上的动量则会大部分保留，因此，其散射角通常会呈现出超镜面反射分布，并且末态的平动能要远小于所谓硬立方模型的预测值. 本文加深了多肽分子与高取向热解石墨碰撞及其能量转移过程的认识和理解，有助于设计在稀薄大气中收集这类大分子的中性气体浓缩器.

Dynamics Studies of Diglycine Scattering from Highly Oriented Pyrolytic Graphite

The dynamics of neutral diglycine collision with highly oriented pyrolytic graphite (HOPG) were studied by molecular dynamics simulations using a reactive force field. The simulations were performed at an initial incident energy of 481.5 kJ/mol for four different initial incident polar angles of 0o, 20o, 45o, and 70o, and a surface temperature of 677 K. The angular, translational and internal energy, and residence time distributions of the scattered products were determined and analyzed. As a polyatomic molecule, diglycine has several low frequency vibrational modes and shows a rather strong attraction to HOPG, which leads to a long residence time on the surface and facile energy loss, particularly along the normal surface. Since there is significant normal momentum lost while parallel momentum is partially conserved, the scattering angular distribution is found to be generally superspecular and the final translational energies are much lower than the values predicted by the so-called hard-cube model. This study extends our knowledge of collisional energy transfer during collisions of polypeptide molecules with HOPG, which is expected to help the design of a neutral-gas concentrator for the fly-by collection of such molecules in rarefied atmospheres.