Study of the molybdenum dichalcogenide crystals: recent developments and novelty of the P-MoS2 structure.

Abstract

Nontoxicity and economic production have turned some of the molybdenum disulfide (MoS2) polytypes into very interesting thermoelectric materials. Therefore, these materials with privileged applications have urged theoretical and experimental investigation for understanding and development of new crystals for particular applications. We present the results of computational-theoretical studies on the structural, vibrational thermoelectric, and thermodynamic properties of five crystal structures, known and newly developed, of MoS2 based on first-principles density functional theory (DFT). While all crystals of MoS2 were explored by undertaking several methods, the DFT method corrected for dispersion interaction (DFT-D2) confirmed the production of the cell parameters closer to the experimental. The variation of the bandgap and density of states (DOS) in all structures represents crystals comprising both semiconductors (2H- and 3R-MoS2 crystals) and metals (1T-, P-MoS2, and FCC-MoS2). According to spectroscopic studies, two typical [Formula: see text] and [Formula: see text] Raman peaks are indicators of in-plane and out-of-plane vibrational modes of S atoms. From the two newly reported crystals (P-MoS2 and FCC-MoS2), P-MoS2 exhibits exclusive thermoelectric properties (within 300-1000K) such as high electrical conductivity, Seebeck coefficient, and low thermal conductivity. The thickness dependence of thermoelectric properties in 1T-, 2H-, and 3R-MoS2 crystals is substantiated. A low thermal conductivity at room temperature along with an extremely high power factor at 1000K exhibited by P-MoS2 suggests P-MoS2 crystal as a potential thermoelectric material. Finally, the present computations can introduce P-MoS2 crystal as a new thermoelectric material with unique and extraordinary properties.