Comparative study of polytype 2H-MoS2 and 3R-MoS2 systems by employing DFT

The structural, electronic, vibrational and thermodynamic calculations were performed on one of the transition metal dichalcogenides such as molybdenum disulphide named bulk 2H-MoS2, single layer 2H-MoS2 and 3R-MoS2 systems. The dispersion corrected density functional theory (DFT-D) has been employed for polytype layered 2H-MoS2 and 3R-MoS2 morphologies. It is found that the electronic band gap in single layer 2H-MoS2 (1.658 eV) structure is found to be higher than that of bulk 2H-MoS2 (0.861 eV). The electronic band gap (1.416 eV) of 3R-MoS2 is found to be lesser than that of single layer 2H-MoS2 but greater than that of bulk 2H-MoS2. The vibrational properties were also performed using the supercell approach and calculated modes of vibration demonstrate an excellent agreement with available experimental results. In addition, thermodynamic potentials and specific heat at constant volume were also calculated on the basis of harmonic approximation to investigate their dependence on temperature.