体心立方金属的色散曲线

Dispersion Curves for BCC Metals

为固体材料的声子色散实验提供了判断和指导依据,把两体中心势和晶格动力学理论相结合,导出了力常数和动力学矩阵元的具体表达式,研究了体心立方金属Ta、W和Nb沿[00ζ]、[0ζζ]和[ζζζ]3个对称方向的声子色散曲线。结果表明:沿[00ζ]、[0ζζ]和[ζζζ]方向,Ta、W和Nb的色散曲线非常相似,只是数值上各有差异;3种金属沿[00ζ]和[ζζζ]2个对称方向上均有简并现象;在长波长附近(Γ点)出现声子软化;在相同的对称方向上,3种体心立方金属Ta、W和Nb的频率随原子质量的减小而依次增加。

The atomic force constants and the elements of the dynamical matrix were derived,and then dispersion curves for bcc metals Ta,W and Nb along symmetry directions[00ζ],[0ζζ]and[ζζζ]respectively were calculated by combining the two-body central potential with the theory of lattice dynamics.The results show that the calculated dispersion curves have a very similar shape along[00ζ],[0ζζ]and[ζζζ]direction.although the actual degree varies somewhat.Along both[00ζ]and[ζζζ]directions, two transverse modes T1 and T2 merge into a transverse mode T for the three metals.The phonon softening phenomenon exists near long wavelength（T point）.The vibration frequency along the same symmetry direction increases for Ta.W and Nb successively with the mass of Ta,W and Nb decreasing successively.It provides a base for judging and guiding the phonon dispersion experiment of solid materials.