Vibration of Zinc Oxide Nanowires in Electric Field

This paper studies the vibration of Zinc oxide (ZnO) nanowires in electric field via molecular dynamics (MD) simulation and continuum beam models. First, the size effects of the equivalent Young’s modulus and piezoelectric constant of ZnO nanowires are obtained by MD simulation and characterized by core-shell model. The piezoelectric constants of ZnO nanowires decrease with the rising of the size of cross section. The equivalent tensile and bending Young’s modulus of ZnO nanowires in polarization direction increases with the increasing of the cross section size. The equivalent tensile and bending Young’s modulus in polarization direction predicted by core-shell model is in good agreement with MD simulation. Then, the vibration of the cantilevered ZnO nanobeam is simulated by MD. When the cross section size becomes larger, the vibration frequencies predicted by continuum theory coincide with those obtained by MD simulation better. Finally, the effect of electric field on vibration frequency of a ZnO nanowire is studied by MD simulation and continuum beam models. It is found that the natural frequencies rise with the increasing of electric field for the case of positive electric field in polarization direction. But the natural frequencies will decrease with the increasing of negative electric field when the intensity of the electric field is relatively weak. The natural frequency is hard to be obtained when the phase transition is occurring in relatively strong negative electric field. The vibration frequencies of the cantilevered Timoshenko beam with axial force due to the effects of electric field are obtained. The frequencies obtained by Timoshenko beam model agree with MD results very well. The vibration frequencies of the continuum theory agree with MD results better when the size of the cross section increases. The vibration frequencies of the ZnO nanowire keep constant when the direction of electric field is perpendicular to the polarization direction.