Estimation of Effective Parameters for the Transition-Metal Complexes by Mapping Self-Interaction Correction onto GGA+U

<div><div>We propose a method to calculate the Hubbard U parameter in GGA+U or the α pa</div><div>rameter in the atomic self-interaction correction (ASIC) scheme for transition-metal</div><div>d orbitals by mapping the self-interaction correction (SIC) onto GGA+U, which is</div><div>suitable for atom-centered basis sets. SIC can offer a substitute for the Hubbard</div><div>U parameter in GGA+U, although its usage should be limited considering the dif</div><div>ferences between GGA+U and SIC. Approximations to reduce computational cost</div><div>for self-interaction (SI) corrected localized orbitals are deduced from the properties</div><div>of the unitary transformation in SIC and the atomic likeness of molecular orbitals</div><div>dominated by transition-metal d orbitals, and the parameters are obtained from the</div><div>approximate forms of the localized orbitals. First-row transition-metal complexes</div><div>were tested, and the results are comparable to experimental measurements and pre</div><div>vious calculations. Our method does not guarantee better results than those of</div><div>the linear response method or hybrid functionals, but mapping from SIC suppresses</div><div>overestimation of the U parameter to obtain proper geometries and energies for Fe</div><div>porphyrin-imidazole, Fe-porphyrin-CO and FeO2 modeling</div></div>

Estimation of Effective Parameters for the Transition-Metal Complexes by Mapping Self-Interaction Correction onto GGA+U

<div><div>We propose a method to calculate the Hubbard U parameter in GGA+U or the α pa</div><div>rameter in the atomic self-interaction correction (ASIC) scheme for transition-metal</div><div>d orbitals by mapping the self-interaction correction (SIC) onto GGA+U, which is</div><div>suitable for atom-centered basis sets. SIC can offer a substitute for the Hubbard</div><div>U parameter in GGA+U, although its usage should be limited considering the dif</div><div>ferences between GGA+U and SIC. Approximations to reduce computational cost</div><div>for self-interaction (SI) corrected localized orbitals are deduced from the properties</div><div>of the unitary transformation in SIC and the atomic likeness of molecular orbitals</div><div>dominated by transition-metal d orbitals, and the parameters are obtained from the</div><div>approximate forms of the localized orbitals. First-row transition-metal complexes</div><div>were tested, and the results are comparable to experimental measurements and pre</div><div>vious calculations. Our method does not guarantee better results than those of</div><div>the linear response method or hybrid functionals, but mapping from SIC suppresses</div><div>overestimation of the U parameter to obtain proper geometries and energies for Fe</div><div>porphyrin-imidazole, Fe-porphyrin-CO and FeO2 modeling</div></div>

Can We Safely Obtain Formal Oxidation States from Centroids of Localized Orbitals?

The use of centroids of localized orbitals as a method to derive oxidation states (OS) from first-principles is critically analyzed. We explore the performance of the closest-atom distance criterion to assign electrons for a number of challenging systems, including high-valent transition metal compounds, π-adducts, and transition metal (TM) carbenes. Here, we also introduce a mixed approach that combines the position of the centroids with Bader’s atomic basins as an alternative criterion for electron assignment. The closest-atom criterion performs reasonably well for the challenging systems, but wrongly considers O-H and N-H bonds as hydrides. The new criterion fixes this problem, but underperforms in the case of TM carbenes. Moreover, the OS assignment in dubious cases exhibit undesirable dependence on the particular choice for orbital localization.