Ab initio investigation of structural stability and exfoliation energies in transition metal dichalcogenides based on Ti-, V-, and Mo-group elements

In this work, we report an ab initio investigation based on density functional theory of the structural, energetic, and electronic properties of 2D layered chalcogenides compounds based in the combination of the transition-metals (Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W) and chalcogenides (S, Se, Te) in three polymorphic phases: trigonal prismatic (2H), octahedral (1T), and distorted octahedral (1T(d)). We determined the most stable phases for each compound, verifying the existence of the 1T(d) phase for a small number of the compounds and we have also identified the magnetic compounds. In addition, with the determination of the exfoliation energies, we indicated the potential candidates to form one layer material and we have also found a relation between the exfoliation energy and the effective Bader charge in the metal, suggesting that when the materials present small exfoliation energies, it is due to the Coulomb repulsion between the chalcogen planes. Finally, we analyzed the electronic properties, identifying the semiconductor, semimetal, and metal materials and predicting the band gap of the semiconductors. In our results, the dependence of the band gap on the d-orbital is explicit. In conclusion, we have investigated the properties of stable and metastable phases for a large set of TMD materials, and our findings may be auxiliary in the synthesis of metastable phases and in the development of new TMDs applications.