A new (2 × 1) dimerized structure of monolayer 1T-molybdenum disulfide, studied from first principles calculations.

The geometric, electronic, and vibrational properties of monolayer 1T-molybdenum disulfide (MoS2) have been studied by using the first-principles calculations. A new (2 × 1) dimerized structure of monolayer 1T-MoS2, called as 1T'-MoS2, has been found, which is semi-conducting and more stable than the previously found ones. Interestingly, a semiconductor-metal transition is found under an applied tensile strain at about 4% or a compressive strain at about 5%, while the dimerization structure has been retained under both the tensile and compressive strains. Moreover, the vibrational properties of three kinds of monolayer MoS2, i.e., the 1T-MoS2, 1T'-MoS2, as well as the 1H-MoS2, have been studied, based upon which the different isomer structures of monolayer MoS2 can be easily distinguishable in experiments by analyzing their characteristic Raman spectra.