Abstract

Introduction. The compound Cu₆PS₅Br belongs to the large family of complex chalcohalides crystallizing in the argyrodite structures. At ambient temperature, the crystals under investigation are characterized by high symmetry: cubic syngony, space group F–43m, lattice parameter a = 9.708 Å. The main peculiarity of the copper-containing argyrodites is high solid-state ionic conductivity of the Cu⁺ ions, which makes it possible to use these argyrodite crystals as functional electronic materials.
Purpose. The main goal of the present work was to develop (within the superspace symmetry concept) the program suitable for theoretical calculation of the phonon spectra for the Cu₆PS₅Br argyrodites and to conduct the relevant calculations.
Methods. In the present study, the crystal structure of the Cu₆PS₅Br argyrodites have been analyzed and described by using the superspace symmetry concept.
Results. The program operating under the Maple environment and suitable for theoretically calculating the phonon spectra of the Cu₆PS₅Br argyrodite crystals has been developed. Zone structures have been calculated and presented for a series of model Сu₆PS₅Br phases. The eigenvalues of the generalized dynamic matrix have been found, and the dispersion dependencies have been built for the directions Г – X – M – R – Г – M of the Brillouin zone

Keywords: argyrodites, crystal structure, protocrystal, phonon spectrum, Maple

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