Electronic Band Structures of Molybdenum and Tungsten Dichalcogenides by the GW Approach

Molybdenum and tungsten dichalcogenides, MX2 (M = Mo and W; X = S and Se), characterized by their quasi-two-dimensional layered structure, have attracted intensive interest due to their intriguing physical and chemical properties. In this work, quasi-particle electronic properties of these materials are investigated by many-body perturbation theory in the GW approximation, currently the most accurate first-principles approach for electronic band structure of extended systems. It is found that the fundamental band gaps of all of these materials can be well described by the GW approach, and the calculated density of states from GW quasi-particle band energies agree very well with photoemission spectroscopy data. Ionization potentials of these materials are also studied by combining the slab model using density functional theory and GW correction. On the basis of our theoretical findings, we predict that none of the materials in MX2 (M = Zr, Hf, Mo, and W; X = S and Se) in their bulk form can be directly used as the photocatalyst for overall photosplitting of water because their VBM and CBM energies do not match the redox potentials of water oxidation and reduction, which, however, can be changed by forming nanostructures, especially for MoS2.