二维单层原子晶格振动的研究

RESEARCH ON THE LATTICE VIBRATION OF TWO-DEMENSIONAL SINGLE ATOM LAYER

构建了体心立方结构金属Ta、W和Mo的二维单层原子的晶格振动模型,在此基础上把原子势函数和晶格动力学理论相结合,用Matlab语言编辑程序模拟了Ta、W和Mo沿ГΧ、ГM和ΧM 3个对称方向的声子色散曲线,并对这些曲线进行了分析.结果表明:Ta、W和Mo3种金属二维单层原子的声子色散曲线非常相似,只是数值上有些差异;沿ГΧ、ГM和ΧM 3个对称方向上,3种金属均有两个独立模,其中在ГΧ和ГM方向上两个独立模分别是纵波模和横波模,然而在ΧM方向上的两个独立模既不是横波模也不是纵波模;在短波长附近(Γ点)观测到了声子软化现象;在同一对称方向上,3种体心立方金属二维单层原子的振动频率随原子质量的增大而依次减小.

Phonons dispersion curves for Bcc metals Ta,W and Mo along symmetry directions ГΧ,ГM and ΧM respectively,have been simulated using matlab computer language by combining the atomic potential function with the theory of lattice dynamics based on the lattice vibration model of two-demensional single atom layer,and then we analyse the dispersion curves.The results show that the dispersion curves of Ta,W and Mo are very similar to each other although the actual degree of fit varies somewhat.Along ГΧ,ГM and ΧM,there are tree vibration modes for Ta,W and Mo respectively.Where along ГΧ and ГM directions the vibration modes are longitudinal mode and transverse mode respectively,however along ΧM direction two vibration modes are neither longitudinal mode nor transverse mode.The phonon softening phenomenon exists near Г point.The vibration frequency along same symmetry direction increases for Ta,W and Mo successively with the mass of Ta,W and Mo decreasing successively.