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

Abstract

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 energy, 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. arXiv:1903.08112v1 [cond-mat.mtrl-sci]

Nanoscale Friction Behavior of Transition-Metal Dichalcogenides: Role of the Chalcogenide

“…Friction contrast between the TMDs can also arise from differences in out of plane deformation which causes bending and stretching of the lattice and acts to enhance static friction. 15,33 An analysis of the out of plane deformation in the simulations revealed that TMD deformation increased with chalcogen size from S to Te (see Figure SI5), in agreement with the trends in the out of plane elastic constants reported by DFT calculations previously, 34,35 but opposite our friction results. Lastly, we investigated the potential effect of contact quality 36 for a subset of the MD simulations by extracting and analyzing the forces on tip atoms, but the results were again not consistent with the observed friction trend.…”

MoS2and Janus (MoSSe) based 2D van der Waals heterostructures: emerging direct Z-scheme photocatalysts

“…The vdW HTSs have been formed with monolayer of MoS 2 (or MoSSe) along with that of WS 2 , ZrS 2 , HfS 2 , TiS 2 , HfO 2 , T-PtO 2 and T-SnO 2 , in vertical alignment. The specifications of the monolayers (see lattice parameters in SI) corroborate with the existing literature 52,72,73 . All the monolayers are constituted as 2 × 2 × 1 supercell (24 atoms) except ZrS 2 and HfS 2 , where √ 3 × √ 3 × 1 supercell consists of 21 atoms.…”

Room-temperature intrinsic ferromagnetism in epitaxial CrTe2 ultrathin films

“…1d ). The diffraction pattern with perpendicular constant c = 6.13 Å is matched to the (001) crystal planes of 1T-type hexagonal structure explored experimentally ( a = 3.79 Å, c = 6.10 Å) 20 , rather than those of the 2H phase ( a = 3.49 Å, c = 13.64 Å) 29 . We note that the magnetic exchange coupling is sensitive to the lattice parameters.…”