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Instal the new Electron 25.3.22/18/2024 10 In addition, SRP density functionals developed for one specific system have been shown to be transferable to a chemically similar system in a number of instances. 10 The SRP-DFT approach has predictive power to the extent that an SRP functional developed by reproducing one experiment on a particular system is required to describe at least one other experiment on the same system with quantitative accuracy and will usually also describe additional experiments on the same system with such accuracy. To overcome these shortcomings, a semi-empirical DFT approach called the specific reaction parameter approach to DFT (SRP-DFT) has been implemented and demonstrated to provide chemically accurate barrier heights E b (accuracy better than 1 kcal/mol) for molecule–metal surface reactions. Both functionals provided barrier heights for the energetically lowest lying transition state that are within 1 kcal/mol of the DMC value. RPBE-vdW-DF and BEEF-vdW were found to perform quite well even in terms of absolute numbers. The comparison shows that all selected functionals yield a rather accurate description of the variation of barrier heights with impact site and orientation, although their absolute values may not be accurate. To this end, barrier heights computed with selected functionals at the generalized gradient approximation (GGA) and meta-GGA levels are compared to the DMC results. Our present goal is twofold: first, to provide accurate barrier heights for the two lowest lying transition states of the system, and second, to assess whether density functionals are capable of describing the variation of barrier height with molecular orientation and impact site through a comparison with DMC barriers. Barrier heights have been computed for six geometries. To provide benchmark barrier heights with a high-quality method, diffusion Monte Carlo (DMC) is applied to H 2 + Al(110). Density functional theory can be utilized to generate a potential energy surface, but with presently available functionals, the results are not yet accurate enough. Reactions of molecules on metal surfaces are notoriously difficult to simulate accurately.
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