Single crystals of Ir2S3 (diiridium trisulfide) and Rh2S3 (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. Ir2S3 and Rh2S3 had similar unit-cell parameters and bond distances. The atomic displacement parameter (MSD: mean-square displacement) of each atom in Ir2S3 was considerably smaller than that in Rh2S3. The Debye temperatures (ΘD) estimated from the observed MSDs for the Ir, S1 and S2 sites in Ir2S3 were 259, 576 and 546 K, respectively, and those for Rh, S1 and S2 in Rh2S3 were 337, 533 and 530 K, respectively. The bulk Debye temperature for Ir2S3 kashinite (576 K) was found to rank among the higher values reported for many known sulfides. The bulk Debye temperature for Rh2S3 bowieite (533 K) was lower than that for Ir2S3 kashinite, which crystallizes in the early sequences of mineral crystallization differentiation from the primitive magma in the Earth's mantle.
Keywords: Debye temperature; bowieite; crystal structure; iridium; kashinite; rhodium; sulfide.