Nonempirical Meta-Generalized Gradient Approximations for Modeling Chemisorption at Metal Surfaces.

We assess the accuracy of popular nonempirical GGAs (PBE, PBEsol, RPBE) and meta-GGAs (TPSS, revTPSS, and SCAN) for describing chemisorption reactions at metal surfaces. Except for RPBE, all the functionals tend to overbind the adsorbate significantly. We then propose a nonempirical meta-GGA, denoted as RTPSS, that is based on RPBE in the same way that TPSS is based on PBE. The RTPSS functional remedies the overbinding problem and improves the description of chemisorption energies. As an example of an application of RTPSS, we study the adsorption of CO on Cu surfaces (a notably difficult problem for semilocal functionals) and find that RTPSS is the only tested functional that predicts accurate chemisorption energies and the preferred adsorption site of CO. Although RTPSS gives an accurate description of chemisorption, nonlocal correlation may be necessary to describe physisorption if long-range van der Waals interactions are involved (however, this is true for semilocal functionals in general). We suggest that RTPSS can be a useful meta-GGA for studying chemisorption processes and mechanisms of heterogeneous catalysis.