Joint experimental and theoretical study of PbGa₂S₄ under compression

The effect of pressure on the structural, vibrational, and optical properties of lead thiogallate, PbGa₂S₄, crystallizing under room conditions in the orthorhombic EuGa₂S₄-type structure (space group Fddd), is investigated. The results from X-ray diffraction, Raman scattering, and optical-absorption measurements at a high pressure beyond 20 GPa are reported and compared not only to ab initio calculations, but also to the related compounds α'-Ga₂S₃, CdGa₂S₄, and HgGa₂S₄. Evidence of a partially reversible pressure-induced decomposition of PbGa₂S₄ into a mixture of Pb₆Ga₁₀S₂₁ and Ga₂S₃ above 15 GPa is reported. Thus, our measurements and calculations show a route for the high-pressure synthesis of Pb₆Ga₁₀S₂₁, which is isostructural to the stable Pb₆In₁₀S₂₁ compound at room pressure.