Strain effect on the electronic properties of 1T-HfS2 monolayer

We perform first-principles based on the density function theory to investigate electronic and magnetic properties of 1T-HfS2 monolayer with biaxial tensile strain and compressive strain. The results show that HfS2 monolayer under strains doesn't display magnetic properties. When the strain is 0%, the HfS2 monolayer presents an indirect band gap semiconductor with the band gap is about 1.252 eV. The band gap of HfS2 monolayer decreases quickly with increasing compressive strain and comes to zero when the compressive strain is above -7%, the HfS2 monolayer system turns from semiconductor to metal. While the band gap increases slowly with increasing tensile strain and comes to 1.814 eV when the tensile strain is 10%. By comparison, we find that the compressive strain is more effective in band engineering of pristine 1T-HfS2 monolayer than the tensile strain. And we notice that the extent of band gap variation is different under tensile strain. The change of band gap with strain from 1% to 5% is faster than that of the strain 6-10%. To speak of, the conduction band minimum (CBM) is all located at M point with different strains. While the valence band maximum (VBM) turns from Gamma point to K point when the strain is equal to and more than 6%.