改进分析型嵌入原子法在W(100)表面声子谱中的应用

在表面晶格动力学理论的框架下,采用改进分析型嵌入原子法模型模拟W(100)表面沿(Γ)(L) 、(L)(M) 和(Γ)(M)对称方向上的声子色散频谱,并计算不同对称点处的极化矢量.按照表面模的判定依据和标记方法绘制不同对称方向上的表面模,并讨论表面模的分布范围和模式耦合现象.基于计算所得的极化矢量,构建近表面原子层的振动态分布,分析不同对称方向上表面模的局域特征和极化方式.以极化矢量为考察对象,直观、形象地展示了表面模色散支之间的避免交叉现象和独立性实交叉现象.

Application of the modified analytic embedded atomic method in W(100) surface phonon spectrum

Based on the theory of surface lattice dynamics,the surface phonon spectrums along three symmetrical directions ofΓL,LM andΓM are simulated for the W(100)surface by using the modified analytic embedded atom method.The polarization vectors at different symmetrical points are also calculated.According to the criterion and marking method of surface mode,the surface modes along different symmetrical directions are drawn,the distribution range and mode coupling of surface modes are discussed as well.The vibration frequencies of surface modes calculated by us have been compared to available experimental datum and some theoretical values correspondingly.The results display that the present results are general agreement with the referenced experimental or theoretical results.Based on the calculated polarization vector,the surface vibration states are constructed for the atomic layers in the neighboring surface.And the polarization and local features of the surface modes along different symmetrical directions are analyzed.The results show that there are some coupling phenomena between surface mode dispersion,such as avoid crossing and independence crossing.The avoid crossing is found between the surface-mode branch S1 and the surface-mode branch S2 nearζy=0.32 along LM direction.In the region,going from L to M,S1 changes from y polarization to z polarization,and S2 changes from z polarization to y polarization.The independence crossings exist between surface-mode branch S1 and surface-mode branch S2 atζx=0.5 alongΓL direction,and surface-mode branch S2 and surface-mode branch S3 atζx=0.5 along LM direction,respectively.Before and after the crossings,the polarization and local features of the surface modes have not changed.Inspection of the polarization vectors,the coupling phenomena are iconically demonstrated.