  The stability of Lithium intercalated 2H- and 1T allotropes of Molybdenum
disulfide (LixMoS2) is studied within a density-functional theory framework as
function of the Li content (x) and the intercalation sites. Octahedral
coordination of Li interstitials in the van der Waals gap is found as the most
favorite for both allotropes. The critical content of Lithium, required for the
initialization of a 2H->1T phase transition is estimated to x ~ 0.4. For
smaller Li contents the hexagonal 2H crystal structure is not changed, while
1T-LixMoS2 compounds adopt a monoclinic lattice. All allotropic forms of
LixMoS2 - excluding the monoclinic Li1.0MoS2 structure - show metallic-like
character. The monoclinic Li1.0MoS2 is a semiconductor with a band gap of 1.1
eV. Finally, the influence of Li intercalation on the stability of multiwalled
MoS2 nanotubes is discussed within a phenomenological model.
