多晶银纳米线拉伸变形的分子动力学模拟研究

Molecular dynamics simulation of polycrystal silver nanowires under tensile deformation

纳米尺度金属Ag以其独特的导电和导热性,广泛应用于微电子、光电子学、催化等领域,特别是在纳米微电极和纳米器件方面的应用.本文采用分子动力学方法模拟了不同晶粒尺寸下多晶银纳米线的拉伸变形行为,详细分析了晶粒尺寸对多晶银纳米线弹性模量、屈服强度、塑性变形机理的影响.发现当晶粒尺寸小于13.49 nm时,多晶Ag纳米线呈现软化现象,出现反Hall-Petch关系,此时的塑性变形机理主要以晶界滑移、晶粒转动为主,变形后期形成五重孪晶;当晶粒尺寸大于13.49 nm时,塑性变形以位错滑移为主,变形后期产生大量的孪晶组织.

Metal silver in the nanoscale range is widely used in the felds,such as microelectronics,optoelectronics,catalysis etc.,due to its unique electrical and thermal conductivity,especially in nano-electrodes and nano-devices.Tensile deformation behavior of polycrystalline silver nanowires,in various grain size,is simulated using molecular dynamics method.Efect of grain size on elastic modulus,yield strength,and plastic deformation mechanism of polycrystalline silver nanowire is analyzed in detail.Results indicate that polycrystalline silver nanowires show a softening for grain sizes smaller than 13.49 nm,a reverse Hall-Petch relationship.At this stage,the plastic deformation is dominated by ‘sliding＇ at the grain boundaries and rotating of grains;moreover,a fve-fold twin is formed at the later stage of deformation.While the plastic deformation mechanism changes to dislocation sliding,when the grain size is larger than 13.49 nm,and a large number of twins are formed at the later stage of deformation.