【摘要】 本文采用中子非弹性相干散射获得GaAs单晶沿三个高对称方向传播之所有纵声支（LA）和横声支（TA）的声速,以及独立的弹性常数:C₁₁=12.20,C₁₂=5.60,C₄₄=5.86(×10¹¹dyn/cm²)。并根据“一级空间色散”唯象理论,讨论了Td点群类晶体,[ζζ0]方向纵、横声学支声子发生耦合的现象与原由。实验与理论计算都表明,这种纵（LA）、横（TA）耦合对其声速的影响,与横、横声学支声子间耦合效应（即旋声性）比较是很不相同的,尽管他们都来自空间色敢的一级展开系数d_ijo纵、横耦合引起声速的劈裂是一个很难从现有实验中观察得到的二阶小量。更多还原

【Abstract】 Dispersion relations of acoustic phonons in region of small wave vector were measured in crystal GaAs by using of coherent inelastic neutron scattering. All velocities of longitudinal and transverse acoustic (LA and TA) phonons along three crystallographic axes have been obtained from the dispersion relations. Three inder-pendently elastic constants were deduced to be C11 = 12.20, C12 = 5.60, C44 = 5.86 (in unit 1011dyn/cm2) from the experimental results. The origin of the coupling between LA and TA phonons propagating along (ζζ 0) axis in the crystal of point group Td was investigated according to "the first-order spatial dispersion" phenomenological theory. The experimental result and theoretical calculation showed that the effect of coupling between LA and TA phonons on velocities of these phonons seems to be too small to be observed from present experiment. This effect is considered to be different from the effect of coupling between two transverse acoustic phonons (i.e. the effect of acoustic activity) which results also from"the first order spatial dispersion", but can be tested by similar experiment.更多还原