Title: Crystal structure, site selectivity, and electronic structure of layered chalcogenide LaOBiPbS3,
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.