Abstract
The dispersion relation for the normal modes of vibration propagating along the [], [], and [] directions in a single crystal of pure gallium arsenide at 296°K has been determined by neutron spectrometry. The frequencies (units cps) of specific modes are (a) (0,0,0): , ; (b) (1,0,0): , , , ; (c) (0.5,0.5,0.5): , , , . The results are analysed in terms of the dipole approximation model. Although a fairly complex version of this model provides a satisfactory description of most of the data, certain significant discrepancies remain. These indicate that the neglect of quadrupole interactions is a serious weakness of the dipole approximation model.
- Received 12 August 1963
DOI:https://doi.org/10.1103/PhysRev.132.2410
©1963 American Physical Society