(569ab) Self-Interaction Correction for Transition Metal Acetate Clusters with Perdew-Zunger Self-Interaction-Correction (PZSIC)

Density functional theory, commonly used for predicting chemical properties, suffers from self-interaction errors, which may result in underprediction of reaction barriers and inaccurate descriptions of properties such as dissociation energy, charge transfer, and others. We employ the Fermi-Löwdin Self-Interaction Correction method to implement the Perdew-Zunger self-interaction correction (PZSIC) energy. Our previous study showed that there is an SIC energy penalty in the PZSIC total energy associated with a 3d⁵ or a 3d¹⁰ shell. This penalty affects the ionization energy of transition metal atoms when an electron is removed from a half- or filled 3d shell. For example, PZSIC-LDA underestimates the second ionization energy of Cu atom by 2 eV. However, the locally scaled SIC (LSIC) method reduces the error and underestimates the ionization energy by only 0.4 eV. We assess the performance of PZSIC and LSIC for predicting the adsorption energies and reaction barriers in various transition metal (TM) acetate cluster models such as Cu(CH₃COO)₂, Zn(CH₃COO)₃, Cr(CH₃COO)₂, Mn(CH₃COO)₃, when the relevant oxidation state of the transition metal changes going from a reactant to a product, such that the energy penalty should appear in the PZSIC total energy difference. We hypothesize that PZSIC will poorly describe these properties when the final product is formed either by oxidizing the TM atom in the reactant containing a 3d⁵ or 3d¹⁰ shell or by reducing the TM atom to 3d⁵ or 3d¹⁰ in the product. We also hypothesize that LSIC will be more accurate than PZSIC. To test this, we will calculate adsorption energies by adsorbing molecules such that the oxidation state of the TM changes, for e.g., Cu in Cu(CH₃COO)₂ changes from +2 to +1. We will also determine reaction barriers of an H atom reacting with the transition metal acetate clusters to reduce the transition metal acetate and form acetic acid.