Does DFT+U mimic hybrid density functionals?

Pragya Verma, Donald G Truhlar

Research output: Contribution to journalArticle

25 Scopus citations

Abstract

This work examines the question of how a Hubbard U correction to a local exchange–correlation functional compares with adding Hartree–Fock exchange to a local functional for both solid-state and molecular properties. We compute a solid-state property, namely the band gap, and thermochemical molecular properties, in particular, main-group bond energies, transition metal–ligand bond energies, and barrier heights, to elucidate whether the DFT+U method mimics hybrid DFT. We find that a calculation with a Hubbard U correction may or may not mimic a hybrid functional—depending on the atom, the subshell, and the property to which it is applied. For band gaps, we find that adding a Hubbard U correction to the valence d orbitals of transition metals increases the band gap, which thereby gets closer to the experimental value, while adding a Hubbard U correction to valence s or p orbitals of main-group elements need not always increase the band gap. For molecular thermochemistry, we find that adding a Hubbard U correction to a local density functional need not have the same effect as adding Hartree–Fock exchange to a local density functional. For example when compared to a DFT calculation with a local exchange-correlation functional, hybrid DFT increases the barrier height in all cases, but DFT+U does not always increase the barrier height. For the band gaps of transition metal monoxides, the Hubbard-corrected results lowered the mean errors significantly and were comparable to what could be achieved with a much more expensive hybrid functional, but for reaction barrier heights and bond energies of molecules, the Hubbard correction was found to lower the mean error by only approximately a kcal/mol. As part of the analysis, we also compare VASP and Gaussian 09 calculations for the same density functional.

Original languageEnglish (US)
Article number182
JournalTheoretical Chemistry Accounts
Volume135
Issue number8
DOIs
StatePublished - Aug 1 2016

Keywords

  • Atomization energy
  • Band gap
  • Barrier height
  • Bond energy
  • Density functional theory
  • Hubbard U correction
  • Molecular thermochemistry
  • Solid-state physics

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