Single-crystal structure refinements and Debye temperatures of Ir 2 S 3 kashinite and Rh 2 S 3 bowieite.

Single crystals of Ir 2 S 3 (diiridium trisulfide) and Rh 2 S 3 (dirhodium trisulfide) were grown in evacuated silica-glass tubes using a chemical transport method and their crystal structures were determined by single-crystal X-ray diffraction analysis. These compounds have a unique sesquisulfide structure in which pairs of face-sharing octahedra are linked into a three-dimensional structure by further edge- and vertex-sharing. Ir 2 S 3 and Rh 2 S 3 had similar unit-cell parameters and bond distances. The atomic displacement parameter (MSD: mean-square displacement) of each atom in Ir 2 S 3 was considerably smaller than that in Rh 2 S 3 . The Debye temperatures (Θ D ) estimated from the observed MSDs for the Ir, S1 and S2 sites in Ir 2 S 3 were 259, 576 and 546 K, respectively, and those for Rh, S1 and S2 in Rh 2 S 3 were 337, 533 and 530 K, respectively. The bulk Debye temperature for Ir 2 S 3 kashinite (576 K) was found to rank among the higher values reported for many known sulfides. The bulk Debye temperature for Rh 2 S 3 bowieite (533 K) was lower than that for Ir 2 S 3 kashinite, which crystallizes in the early sequences of mineral crystallization differentiation from the primitive magma in the Earth's mantle.