Adsorption of successive layers of H2 molecules on a model copper surface: performances of second- to fifth-rung exchange-correlation functionals

Abstract

The interaction of H 2 molecules with a Cu(100) metallic surface has been investigated by DFT approaches using a (H 2 ) n Cu 13 cluster model. Nine exchange-correlation functionals, belonging to the Generalized Gradient Approximations (GGA), meta GGA (mGGA), hybrid Kohn-Sham/Hartree-Fock models, either based on GGAs or mGGAs, range-separated hybrids, and double-hybrid families, have been tested on the chemisorption and physisorption processes involving one or two H 2 layers. The addition of an empirical correction for dispersion has also been tested for some of these functionals. The calculated energies and structural parameters were compared to sophisticated Multi Reference Configuration Interaction including Davidson's correction for quadruple excitations (MRCI+Q).Our results show that among the nine considered exchange-correlation functionals, none can accurately reproduce all processes involved in the successive layers adsorption. Although an hybrid based on a mGGA such as M06-2X can quantitatively describe both the physisorption step and dissociation barriers involved in the adsorption of the first H 2 , it fails to reproduce its chemisorption.On the other hand, significant discrepancies with the reference post-HF data are obtained for the description of the second layer interaction, no matter which functional is considered, outlining the need of improvement and/or development of exchange-correlation functionals suitable for complex systems such as H 2 /H 2 Cu.

Importance of a Nonlocal Description of Electron–Electron Interactions in Modeling the Dissociative Adsorption of H2 on Cu(100)

“…This cluster is completely symmetric with respect to the z axis. Thus, compared to the 13-atom cluster used in previous work, , this choice offers the advantage of avoiding any artificial polarization of the bare metallic cluster along the z -axis. Cu–Cu distances were fixed at the experimental face-centered cubic (fcc) bulk value of 2.56 Å, which corresponds to a lattice constant of 3.592 Å.…”

“…Another way is to keep the accurate quantum chemical treatment but to model the surface by a small cluster. This approach has already been applied to similar problems with a special focus on H 2 physisorption, , but while the electronic structure method is highly accurate, errors could be introduced by the finite size effect of the cluster, which does not allow a proper description of the highly delocalized metal wave functions.…”