Ab initio investigation into the physisorption of noble gases on graphene

The process of physisorption on graphene is of recent interest due to its vast applications, such as an atomic sensor, in electronics and energy storage. Density functional theory (DFT) was used to determine the adsorption energies and distances of X-graphene (X = He, Ne, Ar, Kr, Xe, Rn) systems. The accuracy of DFT relies heavily on the choice of exchange-correlation (xc) functional. Many xc functionals do not fully capture van der Waals (vdW) interactions, if at all, and a correction is needed. The Local Density Approximation (LDA) and various forms of the Perdew-Burke-Ernzerhof (PBE) Generalized Gradient Approximation (GGA) functional, including RPBE and revPBE, were used as well as the SCAN meta-GGA functional. In addition to these functionals, the vdW correction methods of Grimme (D2 and D3) and the revised Vydrov and van Voorhis (rVV10) vdW functional were used to account for dispersion effects. To investigate their accuracy, results were compared to higher level theory computational and experimental results. The revPBE-D3 combination gave the most accurate results for binding energy and distance when compared to computational studies with a mean absolute error (MAE) of in the range of 4.01-12.06 meV and 0.04-0.06 Å, respectively. When compared to experiment, however, SCAN-D3 performed best with a binding distance MAE of 0.04-0.10 Å. These results highlight the strengths and weaknesses of various computational approaches and will help direct future studies.