posted on 2019-01-16, 21:29authored byAdrien Stoliaroff, Stéphane Jobic, Camille Latouche
Herein is reported
a thorough computational investigation on the bulk TiS2 material with the CdI2 structure type and the ideal 1:2
Ti:S stoichiometry. Computations were performed using some of the
most refined models, e.g., a hybrid functional together with dispersion
effects (Grimme’s), the GW ansatz, and the Bethe–Salpether
equation for the optical properties. We showed that switching from
Perdew–Berke–Enzerhof (PBE) to PBE0 leads to a gap opening.
Moreover, our results demonstrate unambiguously that van der Waals
interactions must be properly treated with dispersion effects in order
to retrieve the experimental crystal structure and the appropriate c/a ratio. Indeed, the calculations prove
that when one uses a highly accurate computational protocol, the bulk
hexagonal TiS2 is a semiconductor with a small gap, whereas
using the generalized gradient approximation (GGA) PBE functional
leads to a semimetal. Furthermore, the band structure is significantly
modified when dispersion parameters are taken into account. Pressure
effects were also investigated, and they fully describe the previously
simulated electronic transition behavior of the material, e.g., TiS2 becomes semimetallic under strain.