Institute of Materials Science, University of Tsukuba
○Takuro Kawasaki Ken-ichi Ohshima

Transition-metal intercalated titanium disulfides M_xTiS₂ have various structures and characteristic physical properties depending on the kind or composition of intercalant M. There are several structural reports on M_xTiS₂, but no systematic structural study of Mn_xTiS₂ has done until now. Single crystals of Mn_xTiS₂ were grown in evacuated silica tubes by chemical vapor transport method using iodine as a transport gas. X-ray intensity data were collected at room temperature with the use of an automatic four circle diffractometer. Crystal structures of Mn_xTiS₂(x=0, 0.19, 0.26) were refined and final R-factors are 3.7%, 3.8%, 2.9% where numbers of independent reflections are 576, 464, 307, respectively. The space group of Mn_xTiS₂, P-3m1, is the same as that of TiS₂. Mn atoms occupy octahedral sites in the van der Waals gap randomly. The electron density distributions for the layered compounds by the maximum entropy method have revealed that the covalent bonding exists between Ti and S atoms. On the other hand, no covalent electrons were found between Mn and S atoms. It is understood that Mn atoms show ionic character in the compounds. X-ray diffuse scattering measurements were also performed. The diffuse intensity maxima appeared at (1/2 1/2 1/2), (1/2 0 1/2), (0 1/2 1/2) and its equivalent positions. This reveals that intercalated Mn atoms have a short-range ordering three-dimensionally. We have tried to obtain Warren-Cowley's short-range order parameter for understanding of structural fluctuation in the compound.