铜纳米线拉伸断裂过程的原子尺度分子动力学模拟

基于经典力学势函数的分子动力学模拟方法研究铜纳米线的拉伸断裂过程,并分析断裂前应力、应变和位错行为的关系及断裂后的形貌演化.结果表明:纳米线两端的锥形结构可阻塞位错运动,从而提高其断裂强度;断裂后断口处尖锐的尖端结构形貌会发生自发的回缩和钝化,该过程是尖端上储存的弹性能和的高能结构(如孤立原子、孪晶界和表面弯折等)的自我修复,最终在表面上形成许多能量较低的(111)小平面所致;其物理机理是在温度激活下的能量最小化过程.

Fracture of Cu Nanowire upon Stretch by Atomic Scale Molecular Dynamic Simulation

To explore the fracture mechanism of metal nanowires,a fracture process of Cu nanowire upon stretch was theoretically studied by molecular dynamic (MD) simulations based on embedded atom method (EAM) potential. The relationship between stress, strain and dislocation before fracture as well as the morp
hology evolution after fracture was analyzed. The results demonstrate that the tips on the two ends of the nanowire can stuck the dislocation motion. Then the stacking fault by the first partial dislocation could be annihilated by a full dislocation formed by another partial dislocation. This process can thus enhance the fracture strength. The sharp structure after fracture can retract and become obtuse spontaneously. The atomic scale analysis of the morphology change demonstrates that the fracture is a process of eliminating the high energy structures, such as isolated atoms, twin boundary and surface kink. The surface of the fracture finally emerge many (111) facets with lower energies. Therefore the physical mechanism is attributed to the rule of energy minimization.