纳米晶铜单向拉伸变形的分子动力学模拟

纳米材料是由尺度在1－100nm的微小颗粒组成的体系，由于它具有独特的性能而备受关注。本文简要地回顾了分子动力学在纳米材料研究中的应用，并运用它模拟了平均晶粒尺寸从1．79－5．38nm的纳米晶体的力学性质。模拟结果显示：随着晶粒尺寸的减小，系统与晶粒内部的原子平均能量升高，而晶界上则有所下降；纳米晶体的弹性模量要小于普通多晶体，并随着晶粒尺寸的减小而减小；纳米晶铜的强度随着晶粒的减小而减小，显示了反常的Hall-Petch效应；纳米晶体的塑性变形主要是通过晶界滑移与运动，以及晶粒的转动来实现的；位错运动起着次要的、有限的作用；在较大的应变下（约大于5％），位错运动开始起作用；这种作用随着晶粒尺寸的增加而愈加明显。

Molecular dynamics simulation of the uniaxial tensile deformation of nanocrystalline copper

Nanocrystalline (nc) materials are characterized by a typical grain size from 1 to 100 Din. The uniaxial tensile deformation of computer produced nc coppers is simulated by using molecular dynamics with Finnis-Sinclair potential. The mean grain size of simulated nc coppers is varied within the 5.38 to 1.79 urn range. With grain size decreasing, the mean atomic energy of nc systems and interior grain has increased, but that of grain boundaries has descended slowly. The Young's modulus depends strongly on the grain size, and decreases with decreasing grain size. The simulated nc coppers show a reverse Hall-Petch effect. Most of the plastic- deformation is due to grain boundary sliding, grain boundary motion, and grain rotation, and a minor part is caused by dislocation activities in the grains, which are consistent with experimental results. The dislocation activities begin to play a role in the large strain (over 5%); This role is progressively distinct with gram size increasing.