A Comparative First Principles Study of Two-Dimensional Transition Metal Dichalcogenides

In recent years, studies on the two-dimensional transition metal dichalcogenides have become important since their potentials have useful properties in technological applications. In this respect, the structural, electronic and vibrational properties of the 12 transition metal dichalcogenide (TMD) MX2 (M=Mo,W,Cr,Ni; X=S,Se,Te) sheets are investigated using first-principles calculations. The calculated band structures show that all TMDs are semiconductors with a direct band gap at the K point, except NiX2 ones with indirect band gaps. We find energetic and dynamical stabilities of the MX2 sheets, while NiSe2 lattice becomes unstable with negative frequencies appearing in acoustic modes near the K point. We also discuss the role of average atomic mass and interatomic bonding in determining the Debye temperatures of dynamically stable dichalcogenide sheets.