Institute of Materials Science, University of Tsukuba
○Takuro Kawasaki Ken-ichi Ohshima
Transition-metal intercalated titanium disulfides MxTiS2 have various structures and characteristic physical properties depending on the kind or composition of intercalant M. There are several structural reports on MxTiS2, but no systematic structural study of MnxTiS2 has done until now. Single crystals of MnxTiS2 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 MnxTiS2(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 MnxTiS2, 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.