Simulation Studies Of Vibration Properties And Plastic Deformation Behaviors Of Fivefold Twinned Copper Nanowires

Fivefold twinned nanowires (FTNs) are expected to have more potential applications than twin-free nanowires as key building blocks and active components in various nano-devices due to these superior properties, so it is of important significance to study the mechanical properties of the FTNs. There are three parts of research work in this paper, including the investigation of the elastic modulus, the vibration properties and the plastic deformation.First, atomistic simulations have been conducted to investigate the elastic modulus of FTNs. Simulation results show that the effective Young’s modulus decreases slightly while the effective shear modulus increases slightly with the increase of the wire radius. The effective Young’s modulus and the effective shear modulus will tend to be a stable value respectively when the radius of the FTNs increases to a certain value. Simulation results also show that there exist size dependences of the Young’s and shear moduli due to surface effect. The core-shell composite model can explain the size dependence very well.Second, the vibration behaviors of FTNs have also been investigated based on atomistic dynamics simulations, including longitudinal vibration properties, transverse vibration properties, and torsional vibration properties. Simulation results show that the fundamental torsional and longitudinal vibration frequency is inversely proportional to the wire length and is independent of the wire radius, while the fundamental transverse vibration frequency is inversely proportional to the square of the length and proportional to the wire radius. Furthermore, we show by comparison between simulation results and continuum predictions that, provided that the effective Young’s and shear moduli are used, the classic elastic theory can be applicable to describe the vibration of FTNs. Moreover, for the transverse vibration, the Timoshenko beam model is more suitable since the shear deformation becomes apparent.Finally, plastic deformation behaviors of FTNs have been investigated based on atomistic dynamics simulations. It is found that the plastic deformation of FTNs is dominated by partial dislocation activities. The normalized critical torsional angle corresponding to the onset of plastic deformation increases with the decrease of the wire radius and temperature, while it is almost independent of the wire length and loading rate.