• alloy compounds;
  • Kramers–Kronig transformation;
  • phonon spectra


In this research, the model of five basic structural units (tetrahedra) proposed by Verleur and Barker [Phys. Rev. 149, 715 (1966)] (VB-model) is completed by the statistical approach, which enables us to derive quantitative relations for the oscillator strengths of separate lines. The rule of proportionality of the oscillator strength sum to the content of the components for each dipole pair is developed as a criterion of random distribution of atoms in the lattice. Thus, a proper identification of observed lines was performed. It is shown that the optical-reflection spectra obtained experimentally by the VB-model authors for GaAsP solid solutions can be successfully explained using the VB-model, without the hypothesis of clustering of binary GaAs as well as GaP tetrahedra, which they introduced.