Density functionals combined with van der Waals corrections for graphene adsorbed on layered materials
Article 2020 en
Authors
HT
Hong Tang
SC
Shah Tanvir ur Rahman Chowdhury
JT
Jianmin Tao
Abstract
2 min read
Standard density functionals like Perdew-Burke-Ernzerhof (PBE) or Strongly Constrained and Appropriately Normed (SCAN) need a correction to account for long-range van der Waals (vdW) interaction. The damped Zaremba-Kohn model (dZK) [J. Tao, H. Tang, A. Patra, P. Bhattarai, and J. P. Perdew, Phys. Rev. B 97, 165403 (2018)] starts from a formula for the vdW interaction of a distant atom with a solid surface, both with known dielectric properties, damps this formula at short range, and then treats an adsorbed molecule or atomic layer as a collection of renormalized atoms. We extend this model to graphene adsorbed on semiconducting layered materials [bulk graphite and hBN, and multilayer transition metal dichalcogenides (TMD)] by including the ${C}_{4}$ asymptotic term and multiple electrostatic image effects due to the two surfaces of the substrate slabs in the vdW calculations. The resulting SCAN-vdW-dZK and PBE-vdW-dZK give approximately the same results for the systems considered here, in agreement with available reference values. The predicted binding energies are roughly 25% lower than those from SCAN+rVV10 (revised Vydrov and Van Voorhis 2010), and $\ensuremath{\sim}15%$ lower than those from PBE+rVV10. Since SCAN+rVV10 usually overbinds, the predicted binding energies by SCAN-vdW-dZK and PBE-vdW-dZK are expected to be closer to the true values. The predicted equilibrium binding distances from SCAN-vdW-dZK and PBE-vdW-dZK are slightly larger ($\ensuremath{\sim}0.1\phantom{\rule{0.16em}{0ex}}\AA{}$) than those from SCAN+rVV10, and close to those from SCAN. The binding energy depends upon the number of substrate layers more strongly in vdW-dZK than in rVV10. The ${C}_{4}$-term contributions can be 40% of the total vdW interactions, and the ${C}_{5}$ term contributes about 10%. The effects of images and the back surfaces of slabs can contribute about 4--10%. The vdW interaction energy power laws from the vdW-dZK model for graphene adsorbed on multilayer $\mathrm{Mo}{\mathrm{S}}_{2}$ show slowly varying decay to the pairwise exponent \ensuremath{-}4 with increasing separation $D$, very similar to those obtained from the random-phase approximation and renormalization group approaches by Ambrosetti et al. Both the PBE-vdW-dZK and SCAN-vdW-dZK give a greater increase in interlayer binding energy when the TMD substrate changes from monolayer to four-layer for the graphene/TMD adsorption systems. This is consistent with the relevant electron-energy-loss spectroscopy experimental results showing increased dielectric response from the substrate with increasing substrate layer number.
Discussion(0)
No comments yet. Be the first to comment.