  Using first principles density functional theory calculations, we show a
semimetal to semiconducting electronic phase transition for bulk TiS 2 by
applying uniform biaxial tensile strain. This electronic phase transition is
triggered by charge transfer from Ti to S, which eventually reduces the overlap
between Ti-(d) and S-(p) orbitals. The electronic transport calculations show a
large anisotropy in electrical conductivity and thermopower, which is due to
the difference in the effective masses along the in-plane and out of plane
directions. Strain induced opening of band gap together with changes in
dispersion of bands lead to three-fold enhancement in thermopower for both p-
and n-type TiS2 . We further demonstrate that the uniform tensile strain, which
enhances the thermoelectric performance, can be achieved by doping TiS2 with
larger iso-electronic elements such as Zr or Hf at Ti sites.
