Dresden 2020 – scientific programme

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MA: Fachverband Magnetismus

MA 33: Correlation Theory I

MA 33.2: Talk

Wednesday, March 18, 2020, 09:45–10:00, HSZ 403

A critical assessment of the Hubbard U correction in the calculation of spin state energetics — •Antonio Lorenzo Mariano and Roberta Poloni — Univ. Grenoble-Alpes, CNRS, Grenoble-INP, SIMaP, Grenoble 38000, France

During the past few years there has been much effort towards the accurate description of spin-state energetics in Fe(II) molecular complexes using ab initio methods. Within density functional theory, large deviations in the adiabatic energy difference between low spin (LS) and high spin (HS) are found among different families of XC functionals. Semilocal functionals overstabilize LS while Hartree-Fock overstabilizes HS. Global hybrids, metaGGAs and density-corrected approaches have also been suggested. In our work, we provide a critical assessment of the Hubbard U approach in the description of spin-state energetics and explain the origin of the overly destabilized LS state. Comparing LDA+U and PBE+U results against coupled cluster-corrected multireference perturbation theory values, i.e. CASPT2/CC [1], for a large series of molecular complexes, our study further explains that the reasonably good performance of LDA+U reported so far arises from a cancellation of errors [2]. [1] K. Pierloot et al., J. Chem. Theory Comput., 14, 2446-2455 (2018). [2] L. A. Mariano et al., to be submitted.