氧化锌纳米线振动问题研究

VIBRATION OF ZINC OXIDE NANOWIRES

采用连续介质理论与分子动力学模拟相结合的方法,研究了氧化锌纳米线的振动问题.建立了氧化锌纳米线核壳模型,解释其等效杨氏模量及压电常数的尺寸效应.通过连续介质理论求得氧化锌纳米线振动固有频率,并与分子动力学模拟得到的结果进行对比.研究表明,氧化锌纳米线在极化方向的等效拉伸杨氏模量随着横截面尺寸的增加而逐渐增大,且通过核壳模型分别求得核、壳拉伸杨氏模量.拟合得到的等效拉伸杨氏模量与分子动力学方法获得的等效拉伸杨氏模量符合得很好.根据连续介质理论得到等效弯曲杨氏模量,发现等效弯曲杨氏模量也随着横截面尺寸的增加而增大.氧化锌纳米线极化方向的压电耦合能力比一般压电陶瓷好,压电常数随着横截面尺寸的增加逐渐减小.氧化锌纳米线在不同温度条件下的振动频率没有明显变化,在不同外电场条件下的振动频率有显著变化.分子动力学模拟得到不同横截面尺寸的氧化锌纳米线振动频率不同.根据连续介质理论,求得悬臂Timoshenko梁模型相应尺寸的振动频率,发现横截面的尺寸越大,连续介质理论与分子动力学模拟得到的振动频率越接近.

The vibration of Zinc Oxide（ Zn O） nanowires is studied via molecular dynamics（ MD） simulation and continuum theory. The size effect of equivalent Young＇ s modulus and piezoelectric constant for the Zn O nanowires are described by core-shell model. The equivalent tensile Young＇s modulus of Zn O nanowires in polarization direction increases gradually with the increase of the cross section size. The equivalent tensile Young＇ s modulus predicted by continuum theory is in a good agreement with the MD result. The equivalent bending Young＇s modulus also increases with the increasing cross section size. Meanwhile,the piezoelectric constants of Zn O nanowires are larger than that of piezoelectric ceramics. The piezoelectric constants of Zn O nanowires decrease with the rising of the cross section size. In addition,the vibration of the cantilevered nanobeam made of Zn O is simulated by MD. The vibration frequencies of a Zn O nanowire keep constant at different temperatures.When the cross section size becomes larger,the vibration frequencies predicted by continuum theory get closer to those obtained by MD well.