Electronic structures and charge transfer in lithium and mercury intercalated titanium disulfides

Abstract

Mercury can be intercalated into TiS2 by a reaction between elemental mercury and TiS2 at room temperature. The structure of the obtained compound Hg1.24TiS2 can be described as two non-commensurate monoclinic sublattices. The mercury atoms form metal chains inserted into trigonal prismatic channels created by the expanded TiS2 host lattice. The structural arrangement and interatomic distances for this compound indicate the presence of primarily neutral mercury, with very low charge transfer, and relatively weak HgS interactions. In order to understand this peculiar behaviour, electron band structure calculations have been made using the extended Huckel method and compared with experimental data from different spectroscopies: XAFS, EELS and XPS. Pristine TiS2 and its lithium and mercury intercalated compounds have been investigated. The experimental data are in good agreement with the calculated electronic structures. The main conclusion is that 0.24 electrons are transferred by lithium atom to the TiS2 host structure for the composition Li1TiS2. This transfer is almost equivalent on titanium (0.09 electrons) and sulphur (0.075 electrons per atom). For the mercury intercalated TiS2 phase, both calculations and experimental data show an electronic transfer from mercury to TiS2 very close to zero.