EXAFS study of PbS-SnS solid solution.

The local environment of the Pb atom in Pb(x)Sn(1-x)S solid solution was studied by EXAFS technique. The shortest Pb-S bond length in orthorhombic samples was found to be by approximately 0.2 A 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(7)2v or C(2)2v.