Evaluating the performance of the exchange correlation of the hybrid vdW-DF2, in comparison to rVV10 and PBE functionals: Showcasing the impact on the physical properties of transition metal dichalcogenides

Abstract

Recent investigations have focused on enhancing the modeling of van der Waals (vdW) interactions, particularly through the vdW-DF method. Notably, several advancements in vdW-DF techniques have been introduced, including the PBE+rVV10 approach. These methodologies aim to reduce the discrepancies in binding energies and interaction energy profiles across a specific range of materials, with the intention of achieving broad applicability. However, the effectiveness of these models in relation to energetic materials, such as two-dimensional transition metal dichalcogenides (2D-TMDCs), remains unexamined. The distinctive characteristics of these materials, including their direct band gap, high carrier mobility, excellent stability, and availability, have garnered significant interest in contemporary research. In this study, density functional theory (DFT), as applied within the Quantum ESPRESSO framework, was employed to investigate the impact of the hybrid van der Waals density functional (vdW-DF2) in relation to the rVV10 and Perdew–Burke–Ernzerhof (PBE) correlation potentials. Our results reveal that the implementation of the vdW-DF2 functional significantly affects the characteristics of the compound MoX₂ (where X = S, Se, Te) by alleviating the overestimation of lattice parameters associated with other functionals. Our results reveal that the lattice parameters a and c exhibit variation across different functionals. The PBE functional predicts values of a = 3.68 Å and c = 13.37 Å for MoS₂, while the vdW-DF2 functional provides a = 3.161 Å and c = 12.296 Å, resulting in relative differences (da, dc) of 0.032 and 0.049, respectively. A similar pattern is noted for MoSe₂ where PBE yields a = 3.31 Å and c = 13.00 Å, in contrast to vdW-DF2, which gives a = 3.293 Å and c = 12.918 Å, leading to relative differences of 0.091 and 0.140, respectively. In the case of MoTe₂ PBE estimates a = 3.87 Å and c = 13.91 Å, while vdW-DF2 reports a = 3.551 Å and c = 13.817 Å, with relative differences of 0.881 and 1.095, respectively. In terms of electronic and elastic properties, we demonstrated that the PBE functional reveals superior performance compared to its counterparts. Our findings regarding optical properties provide insights into the material’s suitability for photodetection applications. Interestingly, the results derived from the PBE functional were found to align well with existing experimental data.