Using electronegativity and hardness to test density functionals

Abstract

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Performance of Density Functional Theory for Transition Metal Oxygen Bonds

“…A major advantage of this strategy is the existence of many more systematic experimental data for small molecular systems than for larger homogeneous and heterogeneous catalytic systems. For the diatomic MO and MO + systems studied in this work, almost all of the 60 bond dissociation enthalpies (BDE) are available for all the 3d, 4d, and 5d systems, enabling full account of the periodicities and trends needed for rational catalyst design . In contrast, experimental data for larger catalytic systems are very protocol‐dependent, they are incomplete along the 3d, 4d, and 5d series and are sensitive to defects, solid crystal structure, surface coverage, solvent, pH, and temperature.…”

“…For small systems, accurate quantum‐chemical methods can compute the energies of bond formation and bond breaking, which enables a test of the accuracy of DFT methods used for specific systems. In particular, the use of the BDEs of metal‐ligand bonds are receiving significant attention as best‐practice benchmark properties for chemical reactivity across the d‐block . The success largely relates to the fact that the diatomic M−O BDEs correlate better than any other known single descriptor to the chemisorption energies of pure metal surfaces, with R 2 approaching 0.89 when computed with the same methods, across a range of more than 500 kJ/mol in both O 2 chemisorption energies and M−O BDEs within the d‐block.…”

“…In particular, the use of the BDEs of metal‐ligand bonds are receiving significant attention as best‐practice benchmark properties for chemical reactivity across the d‐block . The success largely relates to the fact that the diatomic M−O BDEs correlate better than any other known single descriptor to the chemisorption energies of pure metal surfaces, with R 2 approaching 0.89 when computed with the same methods, across a range of more than 500 kJ/mol in both O 2 chemisorption energies and M−O BDEs within the d‐block. Coordinative saturation, metal−metal modulations and solvent effects contribute smaller errors to the DFT‐modelled process than the local M−O bond, because the relative M−O bond energies vary by an order of magnitude more than the metal−metal modulating influences, or correspondingly, the trend in cohesive energy changes upon ligand dissociation from different metal surfaces.…”

“…Coordinative saturation, metal−metal modulations and solvent effects contribute smaller errors to the DFT‐modelled process than the local M−O bond, because the relative M−O bond energies vary by an order of magnitude more than the metal−metal modulating influences, or correspondingly, the trend in cohesive energy changes upon ligand dissociation from different metal surfaces. Diatomic M−O BDEs display a residual error of 46 kJ/mol against full surface chemisorption energies when computed with the same method, i. e. the total modulating effects contribute less than 46 kJ/mol to the trend prediction, consistent with the smaller variations in enthalpies of metal atomization relative to M−O bond energies. For comparison, PBE itself has an MAE of 76 kJ/mol for the M−O BDEs, as shown below.…”

“…We recently established a data set of curated experimental BDEs for diatomic transition metal oxides, using experimental trends and state‐of‐the‐art CCSD(T) computations, which reproduce experimental values excellently . We have also shown how CCSD(T) can be used to evaluate full, simple catalytic cycles, again utilizing the fact that the energy errors of the bonds broken and formed during catalysis dominate the energies of the overall catalytic reaction and thus the errors of theoretical catalysis.…”