Application of the Random‐Element Isodisplacement Model to Long‐Wavelength Optical Phonons in CdSexTe1−x Mixed Crystals

Infrared reflection spectra from mixed crystals CdSe x Te 1– x (0 ≦ x ≦ 1) have been investigated in the spectral region from 90 to 300 cm −1 at room temperature. The spectra contain two distinct reststrahlen bands whose strengths and frequencies depend on the composition, x . Using Kramers‐Kronig analysis the frequencies of long wavelength optical phonons were obtained. It is established, that the dependence of the phonon frequencies on the composition of crystals does not show any discontinuity when changing the structure of the mixture from zincblende to wurtzite. The calculations, based on the random‐element isodisplacement (REI) model, of the dependence of long‐wavelength optical phonon frequencies on the composition x are in good agreement with the experimental results.