Benchmarking DFT functionals for Argon adsorption on Ru(0001): assessment of van der Waals corrections for gas-surface interactions.

Accurately describing the interaction of noble gases with metal surfaces remains a significant challenge for theoretical approaches within density functional theory (DFT). Many methods have been proposed to properly incorporate van der Waals effects into DFT, although none of these approaches has demonstrated sufficient accuracy or transferability for modeling the diffraction of rare gases from surfaces. In this work, we present a systematic benchmark of 18 exchange-correlation functionals within DFT for describing the interaction of Ar with the Ru(0001) surface. Our results show that semi-local functionals consistently underestimate the interaction strength, while those including dispersion corrections tend to overestimate it. These discrepancies have direct implications for modeling gas-surface scattering dynamics. Based on our findings, we conclude that Ar/Ru(0001) can serves as a particularly challenging benchmark system for evaluating dispersion corrections in DFT-based surface science simulations.