Crystal structure, site selectivity, and electronic structure of layered chalcogenide LaOBiPbS₃

¹ Graduate School of Science and Engineering, Tokyo Metropolitan University - 1-1, Minami-osawa, Hachioji 192-0397, Japan
² Departmet of Physical Science, Hiroshima University - 1-3-1 Kagamiyama, Higashihiroshima, Hiroshima 739-8526, Japan
³ Faculty of Engineering, Hokkaido University - Kita-13, Nishi-8, Kita-ku, Sapporo, Hokkaido 060-8628, Japan
⁴ Institute of Materials Structure Science, KEK - Tokai 319-1106, Japan
⁵ National Institute of Advanced Industrial Science and Technology (AIST) - Tsukuba, Ibaraki 305-8568, Japan
⁶ Department of Physics, Osaka University - 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan

Received: 27 July 2017
Accepted: 1 September 2017

Abstract

We have investigated the crystal structure of LaOBiPbS₃ using neutron diffraction and synchrotron X-ray diffraction. From structural refinements, we found that the two metal sites, occupied by Bi and Pb, were differently surrounded by the sulfur atoms. Calculated bond valence sum suggested that one metal site was nearly trivalent and the other was nearly divalent. Neutron diffraction also revealed site selectivity of Bi and Pb in the LaOBiPbS₃ structure. These results suggested that the crystal structure of LaOBiPbS₃ can be regarded as alternate stacks of the rock-salt–type Pb-rich sulfide layers and the LaOBiS₂-type Bi-rich layers. From band calculations for an ideal (LaOBiS₂)(PbS) system, we found that the S bands of the PbS layer were hybridized with the Bi bands of the BiS plane at around the Fermi energy, which resulted in the electronic characteristics different from that of LaOBiS₂. Stacking the rock-salt type sulfide (chalcogenide) layers and the BiS₂-based layered structure could be a new strategy to exploration of new BiS₂-based layered compounds, exotic two-dimensional electronic states, or novel functionality.