Role of van der Waals interactions on the binding energies of 2D transition-metal dichalcogenides

Atomically-two-dimensional (2D) materials have out-of-plane van der Waals (vdW) interactions and in-plane covalent bonds, which enables the possibility to exfoliate and reassemble different 2D materials into arbi-trarily stacked heterostructures. Here, we compare the atomic structures, binding energies, and dipole moments of transition-metal dichalcogenides (TMDCs) by different vdW-inclusive density functional theory (DFT) ap-proaches. We found that the selection of the vdW-inclusive approaches largely affects the relaxed structure and the dipole moment of 2D systems. Specially, DFT-D3 takes chemical environments into account and reduces the double-counting effects at medium-range, and provides comparable binding energies for MoS2 with experimental results. This work highlights the importance of dispersion force and provides a guidance for selecting dispersion approaches in 2D device theoretical designs.