First-order Raman scattering from BeO, ZnO, ZnS, and CdS, all having the wurtzite structure ($C_{6v}$), has been investigated. A discussion of the effects of the competition between the long-range electrostatic forces and the short-range forces due to anisotropy in the interatomic force constants on the vibrational spectrum has been included. A series of scattering diagrams are presented showing the geometrical arrangements necessary to observe all the $k=0\mathrm{}$ phonons for this type of crystal structure. In BeO the $E_2$ mode was resolved from the transverse modes for the first time. The assignments of the $E_2$ modes in ZnS differ from previous investigations. From absolute intensity measurements, electro-optic coefficients for BeO, ZnO, and CdS were determined.

• Received 5 December 1968

DOI:https://doi.org/10.1103/PhysRev.181.1351