High-pressure synthesis of boron-rich chalcogenides B12S and B12Se

Two boron-rich chalcogenides B₁₂S and B₁₂Se isostructural to α-rhombohedral boron were synthesized by chemical reaction of the elements at high-pressure – high-temperature conditions. The crystal structures and stoichiometries of both compounds were confirmed by Rietveld refinement of synchrotron X-ray diffraction data and elemental analysis. The experimental Raman spectra of B₁₂S and B₁₂Se were investigated for the first time. All observed Raman bands have been attributed to the theoretically calculated phonon modes, and the mode assignment has been performed.