Performance of a Non-Local van der Waals Density Functional on the Dissociation of H₂ on Metal Surfaces

Abstract

van der Waals functionals have recently been applied to obtain a potential energy surface to describe the dissociation of H2 on Ru(0001), where an improvement was found for computed reaction probabilities compared to experiment, which could not be achieved with the use of other exchange-correlation functionals. It is, however, not yet clear to what extent van der Waals functionals give a better description of other molecule-metal surface systems. In this study, the optPBE-vdW-DF functional is compared to the SRP48 functional, which was originally fitted to describe the dissociation of H2 on Cu(111), in terms of the resulting potential energy surfaces and results of quasi-classical dynamics calculations and their agreement with experiment for different H2-metal surface systems. It is found that overall the optPBE-vdW-DF functional yields potential energy surfaces that are very similar to potential energy surfaces computed with the SRP48 functional. In dynamics calculations the optPBE-vdW-DF functional gives a slightly better description of molecular beam experiments. Also a different dependence of reaction on the rotational quantum number J is found, which is in better agreement with experimental data for H2 dissociation on Cu(111). The vibrational efficacy is found to be relatively insensitive to which of the two functionals is chosen.

Quantum Monte Carlo Calculations on a Benchmark Molecule–Metal Surface Reaction: H2 + Cu(111)

“…For example, in exploratory research investigating the influence of van der Waals interactions on reaction probabilities of H 2 at metal surfaces, it has been found that certain experimental observables are equally well reproduced using the optPBE-vdW-DF functional, which, however, gives a significantly higher reaction barrier for the bridge-to-hollow dissociation of H 2 on Cu(111) of E b = 16.4 kcal/mol. 83 This functional, however, has not yet been as extensively tested on reactive and nonreactive scattering of H 2 and D 2 on Cu(111) as the reference functional cited above. 3,48,84 Therefore, for the time being, the SRP value of 14.5 kcal/mol should be considered the benchmark value.…”

Vibrational Excitation of H2 Scattering from Cu(111): Effects of Surface Temperature and of Allowing Energy Exchange with the Surface

“…Calculations using correlation functionals that describe the van der Waals interaction in at least an approximate way suggest that this should be possible, 84,85 and an empirical potential describing scattering in the van der Waals energy regime and reproducing the resonances is available from potential inversion. 83 Furthermore, an investigation 81 of H 2 + Cu(111) that considered a few experiments on H 2 + Cu(111) also addressed with the SRP and SRP48 functionals showed that these experiments were equally well described with the optimized Perdew–Burke–Ernzerhof van der Waals density functional (optPBE-vdW-DF). 86 This latter functional was not used in the present study as it has not yet been used for quantitative comparison with the same wide range of experiments as the SRP and SRP48 functionals.…”

On the tautomerisation of porphycene on copper (111): Finding the subtle balance between van der Waals interactions and hybridisation

“…The latter is a fundamental aspect of the DFT study of organic and organometallic molecule adsorption on metal surfaces that, despite the latest major vdW functional developments, 25 still demands benchmarking and refinement. One challenge faced in this theoretical area is functional transferability, in the sense that a functional should be valid to describe a wide range of system classes (e.g., molecular and layered crystals [26][27][28] or molecule-metal surface interactions [29][30][31][32] or long and short length scales (e.g., in gas-surface interactions in a dynamical environment 33,34 ), simultaneously.…”