Joint experimental and theoretical study of PbGa 2 S 4 under compression.

The effect of pressure on the structural, vibrational, and optical properties of lead thiogallate, PbGa 2 S 4 , crystallizing under room conditions in the orthorhombic EuGa 2 S 4 -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'-Ga 2 S 3 , CdGa 2 S 4 , and HgGa 2 S 4 . Evidence of a partially reversible pressure-induced decomposition of PbGa 2 S 4 into a mixture of Pb 6 Ga 10 S 21 and Ga 2 S 3 above 15 GPa is reported. Thus, our measurements and calculations show a route for the high-pressure synthesis of Pb 6 Ga 10 S 21 , which is isostructural to the stable Pb 6 In 10 S 21 compound at room pressure.