superlattice, for which a generalized dynamic matrix is constructed, involving an array of eight modulation vectors which determine the dynamic matrices of the protocrystal and mass defect matrices.

Based on the elaborated procedure, the transformation of dispersion of phonon spectra of BaTiO₃-type crystalline structures was studied, the formation of defects in all sites of this structure being simulated. The transformation was analyzed with both conservation and variation of space groups (O_h to D_4h). A detailed analysis of variation of the dispersion curves in the vicinity of the Γ point at small variation of the average is performed for defect structures of А (BaTiOOO_d) and В (BaTiOO_dO_d) type where d determines the position at which vacancies are located. Transitions between the defect-free structure and A or B type structures as well as the transition between these structures are analyzed. Dispersion curve families have been calculated. Complicated transformations of the phonon spectra degeneracies in some point of the Brillouin zone of the A and B type structures are shown to occur in the frequency range near 350 cm^-1 at small variations of average mass characteristics, depending on these variation values.

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