Theoretical unification of hybrid-DFT and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mtext>DFT</mml:mtext><mml:mo> </mml:mo><mml:mo>+</mml:mo><mml:mo> </mml:mo><mml:mi>U</mml:mi></mml:math>methods for the treatment of localized orbitals

Ivády, Viktor; Armiento, Rickard; Szász, Krisztián; Janzén, Erik; Gali, Ádám; Abrikosov, Igor A.

doi:10.1103/physrevb.90.035146

Cited by 58 publications

(54 citation statements)

References 86 publications

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“…With suitably chosen α, the HSE functional can, in many instances, provide a good description of electronic properties ranging from band to Mott-Hubbard insulators as shown in previous work [48,49]. The percentage α of exact-change in hybrid DFT can be semi-quantitatively related to the value of the Hubbard U parameter in DFT+U, with larger values of α (and U) yielding larger optical gaps [48][49][50].…”

Section: Theorymentioning

confidence: 99%

Insulating phases of vanadium dioxide are Mott-Hubbard insulators

et al. 2017

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We present the first comprehensive broadband optical spectroscopy data on two insulating phases of vanadium dioxide (VO 2 ): monoclinic M 2 and triclinic. The main result of our work is that the energy gap and the electronic structure are essentially unaltered by the first-order structural phase transition between the M 2 and triclinic phases. Moreover, the optical interband features in the M 2 and triclinic phases are remarkably similar to those observed in the well-studied monoclinic M 1 insulating phase of VO 2 . As the energy gap is insensitive to the different lattice structures of the three insulating phases, we rule out vanadium-vanadium pairing (the Peierls component) as the dominant contributor to the opening of the gap. Rather, the energy gap arises primarily from intra-atomic Coulomb correlations.

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Section: Theorymentioning

confidence: 99%

Insulating phases of vanadium dioxide are Mott-Hubbard insulators

et al. 2017

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“…Incorrect determination of band gap can, apart from giving wrong estimations of use in electronic materials, also result in the spurious placement of impurity states within the conduction band [124]. A recently developed method, the HSE06+Vw [28][29], intended specifically for this kind of electronic structure and detailed earlier in this thesis has been shown to give improved results through the use of hybrid functionals along with an orbital dependent correction scheme similar to that of LDA+U.…”

Section: Dilute (Tmal)n Alloysmentioning

confidence: 99%

“…The method of hybrid-DFT+Vw was developed by Ivády et al [28][29] and came out of a discovery of similarities between DFT+U and hybrid functionals in terms of corrections to energy and potential. In these papers Ivády et al showed that the correction to exchange energy of the subsystem of correlated orbitals !…”

Section: Hse06+vwmentioning

confidence: 99%

“…In principle that could be done here as well but one method for determining ! self-consistently, provided by Ivády [29], is to make use of and fulfilling the generalized Koopman's theorem (gKT) [30][31][32]. The Koopman theorem states that the KS eigenvalue of the highest occupied (lowest empty) orbital is equal to the change in total energy if an electron is removed (added) to the system assuming all other orbitals remain unchanged.…”

Section: Determining the Parameter !mentioning

confidence: 99%

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Theoretical understanding of stability of alloys for hard-coating applications and design

Lind¹

2015

Linköping Studies in Science and Technology. Dissertations

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The performance of modern hard coating materials puts high demands on properties such as hardness, thermal stability and oxidation resistance. These properties not only depend on the chemical composition, but also on the structure of the material on a nanoscale. This kind of nanostructuring will change during use and can be both beneficial and detrimental as materials grown under non-equilibrium conditions transforms under heat treatment or pressure into other structures with significantly different properties. This thesis aims to reveal the physics behind the processes of phase stability and transformations and how this can be utilized to improve on the properties of this class of alloys. This has been achieved through the application of various methods of first-principles calculations and analysis of the results on the basis of thermodynamics and electronic structure theory.Within multicomponent transition metal aluminum nitride alloys (TMAlN) a number of studies have been carried out and presented here on ways of improving high temperature stability and hardness. Most (TMAl)N and TMN prefer a cubic B1 structure while AlN is stable in a hexagonal B4 phase, but for the purposes of hard coatings the metastable cubic B1 AlN phase, isostructural with the TMN phase is desired. It will be shown how the introduction of additional alloying components, such as Cr, into (TiAl)N changes the thermodynamic stability of phases so that new intermediary and metastable phases are formed during decomposition. In the case of such a (CrAl)N phase it is shown to have greater thermodynamic stability in the cubic phase than the pure AlN, resulting in improved high temperature hardness. Also, the importance of treating not just the binodal decomposition through the formation energy relative to end products but also the impact of spinodal decomposition from its second derivative due to the topology of formation energy surfaces is emphasized in the thesis. The impact of pressure on the AlN phase has also been studied through the calculation of a P-T diagram of AlN as part of a (TiAl)N alloy.During the study of chemical alloying of TM components into AlN the alloying of low concentrations of these TM were treated in great detail. What is generally referred to as the AlN phase in decomposition is not entirely pure and can be expected to contain traces of any alloying components, such as Ti and Cr or whatever other metals may be present. Low concentration alloying of Cr, on the order of 5-10% is also shown to be stable with regard to isostructural decomposition. Detailed analysis of the effect of Ti and Cr impurities in AlN has been carried out along with a systematic search of AlN alloyed with small amounts of other TM components. The impact of these impurities on the electronic structure and thermodynamic properties is analyzed and the general trends will be explained through the occupation of impurity states by d-like electrons.iv Theoretical treatment of such impurities is not straightforward however. AlN is an s-p semiconduct...

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“…Functionals adopted by the condensed matter physics community in the early days of DFT applications to solids were strictly dependent on the electronic density [19,20]; those employed by the chemistry community were instead often defined using linear combinations of Hartree-Fock exchange and density-dependent exchange functionals, which are referred to as hybrid functionals. The latter have also seen many implementations and uses [11,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] in condensed matter physics. One successful example of hybrid functionals is that of the optimally tuned rangeseparated hybrid [39], defined using parameters selfconsistently tuned to enforce the validity of Koopman's theorem [40] for molecules.…”

Section: Introductionmentioning

confidence: 99%

Generalization of Dielectric-Dependent Hybrid Functionals to Finite Systems

et al. 2016

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The accurate prediction of electronic and optical properties of molecules and solids is a persistent challenge for methods based on density functional theory. We propose a generalization of dielectricdependent hybrid functionals to finite systems where the definition of the mixing fraction of exact and semilocal exchange is physically motivated, nonempirical, and system dependent. The proposed functional yields ionization potentials, and fundamental and optical gaps of many, diverse molecular systems in excellent agreement with experiments, including organic and inorganic molecules and semiconducting nanocrystals. We further demonstrate that this hybrid functional gives the correct alignment between energy levels of the exemplary TTF-TCNQ donor-acceptor system.

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Theoretical unification of hybrid-DFT andDFT + Umethods for the treatment of localized orbitals

Cited by 58 publications

References 86 publications

Insulating phases of vanadium dioxide are Mott-Hubbard insulators

Insulating phases of vanadium dioxide are Mott-Hubbard insulators

Theoretical understanding of stability of alloys for hard-coating applications and design

Generalization of Dielectric-Dependent Hybrid Functionals to Finite Systems

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