Abstract
Hybrid density functionals replace a fraction of an underlying generalized-gradient approximation (GGA) exchange description with a Fock-exchange component. Range-separated hybrids (RSHs) also effectively screen the Fock-exchange component and thus open the door for characterizations of metals and adsorption at metal surfaces. The RSHs are traditionally based on a robust GGA, such as PBE (Perdew J P et al 1996 Phys. Rev. Lett. 77 3865), for example, as implemented in the HSE design (Heyd J et al 2003 J. Chem. Phys. 118 8207). Here we define an analytical-hole (Henderson T M et al 2008 J. Chem. Phys. 128 194105) consistent-exchange RSH extension to the van der Waals density functional (vdW-DF) method (Berland K et al 2015 Rep. Prog. Phys. 78 066501), launching vdW-DF-ahcx. We characterize the GGA-type exchange in the vdW-DF-cx version (Berland K and Hyldgaard P 2014 Phys. Rev. B 89 035412), isolate the short-ranged exchange component, and define the new vdW-DF hybrid. We find that the performance vdW-DF-ahcx compares favorably to (dispersion-corrected) HSE for descriptions of bulk (broad molecular) properties. We also find that it provides accurate descriptions of noble-metal surface properties, including CO adsorption.
Highlights
The search for a better computational-theory understanding of small-molecule/substrate and organics/substrate interfaces is directly motivated by technological and environmental challenges
Since the generalized-gradient approximation (GGA) is given by the local value of the density n and of the scaled gradient s, the GGA exchange hole must be approximated in those terms and we introduce a dimensionless representation [25, 132, 142, 160]
We highlight an important point of the AHCX success: we find that AHCX simultaneously have accurate descriptions of molecules, bulk lattice constants, surface properties, and CO adsorption energies; there is no lucky hit for one quantity at the expense of others, compare figure 6 as well as tables 3–5
Summary
The search for a better computational-theory understanding of small-molecule/substrate and organics/substrate interfaces is directly motivated by technological and environmental challenges. In this paper we introduce a new range-separated hybrid (RSH), termed vdW-DF-ahcx, based on the consistentexchange CX version, and having the same correlation description as in the first general-geometry vdW-DF version [51, 52]. We document this for two bulk cases within, while we here provide an example comparison for medium-sized molecules, namely timing information extracted from our study of the C60ISO benchmark set on fullerene isomerizations, (reference [120] includes a presentation of the set) These are just 10 out of the roughly 2300 molecular problems (investigated in multiple functionals) that are part of this AHCX launching work, but they give an impression. The appendix documents robustness of the adsorption-site-preference results with changes in the PP choice while the supplementary information (https://stacks.iop.org/JPCM/34/025902/mmedia) (SI) material provides details of performance characterizations
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