EXAFS study of PbS–SnS solid solution

The local environment of the Pb atom in Pb_xSn_1-xS solid solution was studied by EXAFS technique. The shortest Pb—S bond length in orthorhombic samples was found to be by ≃0.2 Å shorter than in cubic PbS. This indicates that the 6s² lone pair of Pb is stereochemically active in the SnS host. Strong correlations found in the distribution of metal atoms in the second shell show that the orthorhombic samples can be considered as solid solutions with unexpectedly strong short-range order. One can expect that the short-range order in PbSnS₂ may result in formation of superstructures with space groups C_2v⁷ or C_2v².