Heterogeneous catalysts are a critical part of industrial chemistry, primarily as a tool for more economically and ecologically efficient chemical processes. It is thus desirable to develop theoretical methods that can predict trends in catalytic activity and predict active catalyst for industrially important reactions. We have chosen to undertake a benchmarking study of various methods on the dissociation of molecular hydrogen on small gold and silver clusters. The simulation of the reactivity of H2 over small noble metal clusters is interesting both for elucidating the participation of the small clusters and also as a model for the metal-hydrogen interactions in nanoparticles and surfaces. In this study, the mechanism of the dissociation of H2 on Au3 and Ag3 clusters is computed with a high-level of theory, namely CCSD(T)/CBS. Several transition states and isomers with two independent H atoms coordinated to a triatomic cluster have been found. A benchmark study of the performance of DFT methods for the calculation of these mechanisms was perfomed. A wide range of DFT functionals have been selected for this work including a local functional; semi-local functionals; hybrid functionals; range separated hybrid functionals; double-hybrids including the HF-like exchange and MP2-like correlation; and new developed Rung 3.5 functionals including both the exact and semi-local one-particle density matrices. Wave function methods are also included for comparison purposes.


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