六方密排金属晶格振动的改进分析型嵌入原子法研究

Study of Lattice Vibration for HCP Metals by Modified Analytical Embedded Atom Method

在简谐近似下,应用改进分析型嵌入原子法模拟了六方密排结构金属铍、镁和锆沿ΓK、KM、ΓM和ΓA对称方向的声子色散曲线,计算了五个不同对称点处振动态的极化矢量,讨论了原子的振动特征。结果表明:铍、镁和锆三种金属的声子色散曲线非常相似,只是数值不同;沿ΓK、KM和ΓM对称方向,三种金属均有六条独立的色散曲线,每个波矢对应有六种振动态;沿ΓA方向存在四条独立色散曲线,其中OT色散曲线是由OT 1和OT 2色散曲线简并而成。在同一波矢下,OT 1对应的振动态完全在X方向极化,而OT 2相应的振动态完全在Y方向极化,属于两种不同的振动态,相似情况也发生在AT色散曲线中。

In harmonic approximation,the phonon dispersion curves for HCP metals beryllium,magnesium and zirconium along the symmetry directionsΓK,KM,ΓM andΓA were simulated,and the polarization vectors of the vibration states at five different symmetry points were calculated by the modified analytical embedded atom method.And then the vibration characteristics of atoms were discussed.The results showed that the phonon dispersion curves of the metals beryllium,magnesium and zirconium were very similar,but the frequency values were different.The metals had six independent dispersion curves alongΓK,KM andΓM symmetry directions,and each wave vector corresponded to six vibration states.There were four independent dispersion curves alongΓA direction,and the OT dispersion curve was degenerate from the OT 1 and OT 2 dispersion curves.Considered same wave vector,the vibration state OT 1 were completely polarized in the X direction,and the vibration state OT 2 were completely polarized in the Y direction,which belong to two different vibration modes.Similar situations also occured in the AT dispersion curve.