Density Functional Theory in Transition-Metal Chemistry: A Self-Consistent Hubbard U Approach

Department of Materials Science and Engineering , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Physical Review Letters (Impact Factor: 7.51). 10/2006; 97(10):103001. DOI: 10.1103/PhysRevLett.97.103001
Source: PubMed

ABSTRACT Transition-metal centers are the active sites for a broad variety of biological and inorganic chemical reactions. Notwithstanding this central importance, density-functional theory calculations based on generalized-gradient approximations often fail to describe energetics, multiplet structures, reaction barriers, and geometries around the active sites. We suggest here an alternative approach, derived from the Hubbard U correction to solid-state problems, that provides an excellent agreement with correlated-electron quantum chemistry calculations in test cases that range from the ground state of Fe2 and Fe2- to the addition elimination of molecular hydrogen on FeO+. The Hubbard U is determined with a novel self-consistent procedure based on a linear-response approach.

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    • "Such a discrepancy may be resolved when the Hubbard U is determined in a more rigorous self-consistent approach. In this approach, the Hubbard U is determined from the linear response of a series of DFT + U ground states (with a series of trial U values) to the local perturbation until a consistent result is achieved (Kulik et al., 2006). Fig. 9 shows the relative enthalpies of LS, IS, and low-QS HS with respect to high-QS HS (Mg 0.875 Fe 0.125 )SiO 3 in GGA(+U) and LDA (+U) calculation. "
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    ABSTRACT: With the guidance of first-principles phonon calculations, we have searched and found several metastable equilibrium sites for substitutional ferrous iron in MgSiO3 perovskite. In the relevant energy range, there are two distinct sites for high-spin, one for low-spin, and one for intermediate-spin iron. Because of variable d-orbital occupancy across these sites, the two competing high-spin sites have different iron quadrupole splittings (QS). At low pressure, the high-spin iron with QS of 2.3–2.5 mm/s is more stable, while the high-spin iron with QS of 3.3–3.6 mm/s is more favorable at higher pressure. The crossover occurs between 4 and 24 GPa, depending on the choice of exchange-correlation functional and the inclusion of on-site Coulomb interaction (Hubbard U). Our calculation supports the notion that the transition observed in recent Mössbauer spectra corresponds to an atomic-site change rather than a spin-state crossover. Our result also helps to explain the lack of anomaly in the compression curve of iron-bearing silicate perovskite in the presence of a large change of quadrupole splitting, and provides important guidance for future studies of thermodynamic properties of this phase.
    Earth and Planetary Science Letters 05/2010; 294(1-294):19-26. DOI:10.1016/j.epsl.2010.02.031 · 4.73 Impact Factor
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    • "In this approach, the consistency between the response and the DFT+U ground states should be achieved. The Hubbard U determined this way is called self-consistent U (Kulik et al. 2006). This method, however, was not used in calculations reviewed here. "
    Reviews in Mineralogy and Geochemistry 04/2010; 71(1):169-199. DOI:10.2138/rmg.2010.71.09 · 4.76 Impact Factor
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    ABSTRACT: Our density functional theory (DFT) based first principle calculation shows that structural, electronic and optical properties of ZnMnIn2Te4 chalcopyrite type semiconductor are improved by DFT + U functional compared to LDA. These calculations are carried out using plane wave basis and atomic pseudopotentials as implemented in Quantum ESPRESSO. The lattice parameters (‘a’, ‘c’) and tetragonal distortion (η = c/2a) are calculated by energy minimization procedure. The full structural relaxation is carried out within DFT + U. Density of states (DOS) shows that it is n-type semiconductor. The calculated bond lengths show that the system undergoes anion displacement. Optical properties are studied using TB-LMTO method with the input of structural parameters as found from plane wave method using DFT + U.
    Transactions of the Indian Institute of Metals 08/2013; 66(4). DOI:10.1007/s12666-013-0271-9 · 0.62 Impact Factor
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