超高速碰撞成坑特性分子动力学模拟

基于开源分子动力学程序LAMMPS，对直径为4.86 nm的球形铝弹丸以10 km/s超高速撞击半无限厚铝靶进行模拟.弹坑形成的物理过程与超高速碰撞宏观现象相似，弹坑深度与宏观经验公式计算结果基本一致，获得了弹丸头部相对于碰撞点的位移随时间的变化规律；分析了靶板中冲击波传播特性，碰撞初期冲击波阵面传播速度达到12 km/s，随后冲击波传播速度逐渐减小，接近于弹性波速；弹坑周围观测区发生熔化相变，熔化时间持续0.07 ps，熔化层厚度为2.9 nm；弹坑周围观测区冷却速率达到1015 K/s量级，抑制了原子重结晶，最终呈现为固相非晶结构. 

Molecular Dynamics Simulation on Characteristics of Crater Formation Induced by Hypervelocity Impact

Based on the open source molecular dynamics program LAMMPS, hypervelocity impact of a spherical aluminum projectile with a diameter of 4.86 nm on the semi-infinite thick aluminum target at the speed of 10 km/s was simulated. The physical process of crater formation was similar to that from a macroscopic impact. The crater depth was consistent with the data from the macro empirical formula and its variation with time was obtained. The propagation characteristics of the shock wave in the target were analyzed. The propagation speed of the shock wave front reached up to 12 km/s during the initial impact, and then the speed gradually decreased and was close to the elastic wave velocity. The observation region around the crater experienced melting state which lasted about 0.07 ps and had a layer thickness of 29 nm. The cooling rate of the observation region around the crater reached the order of 10¹⁵ K/s which prevented atom recrystallization. The observation region finally turned into a solid phase amorphous structure.