Hubbard-corrected density functional perturbation theory with ultrasoft pseudopotentials

Floris, Andrea; Timrov, Iurii; Himmetoḡlu, Burak; Marzari, Nicola; Gironcoli, Stefano de; Cococcioni, Matteo

doi:10.1103/physrevb.101.064305

Cited by 56 publications

(48 citation statements)

References 107 publications

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“…To capture the Mo d electron localization, both DFT + U [60][61][62][63][64] and the extended DFT + U + V [64,65] Hubbard corrective functionals were adopted. These schemes have been successfully used on a broad variety of cases and proved very effective in improving the structural [77], vibrational [64,[78][79][80][81][82][83][84], and electrochemical [85] properties as well as the phase-stability and transitions of d and f electron systems, notably involving magnetism [86][87][88][89]. Like in many of the works cited above the effective Hubbard interactions (i.e., the on-site U for Mo d states and inter-site V between Mo d and nearest-neighbor O p states) were determined from first-principles linear-response theory [77] using a density functional perturbation theory (DFPT) implementation [90,91].…”

Section: Methodsmentioning

confidence: 99%

Magnetic Energy Landscape of Dimolybdenum Tetraacetate on a Bulk Insulator Surface

Cococcioni

Floris

2021

Applied Sciences

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The magnetic states and the magnetic anisotropy barrier of a transition metal molecular complex, dimolybdenum tetraacetate, are investigated via density functional theory (DFT). Calculations are performed in the gas phase and on a calcite (10.4) bulk insulating surface, using the Generalized-Gradient Approximation (GGA)-PBE and the Hubbard-corrected DFT + U and DFT + U + V functionals. The molecular complex (denoted MoMo) contains two central metallic molybdenum atoms, embedded in a square cage of acetate groups. Recently, MoMo was observed to form locally regular networks of immobile molecules on calcite (10.4), at room conditions. As this is the first example of a metal-coordinated molecule strongly anchored to an insulator surface at room temperature, we explore here its magnetic properties with the aim to understand whether the system could be assigned features of a single molecule magnet (SMM) and could represent the basis to realize stable magnetic networks on insulators. After an introductory review on SMMs, we show that, while the uncorrected GGA-PBE functional stabilizes MoMo in a nonmagnetic state, the DFT + U and DFT + U + V approaches stabilize an antiferromagnetic ground state and several meta-stable ferromagnetic and ferrimagnetic states. Importantly, the energy landscape of magnetic states remains almost unaltered on the insulating surface. Finally, via a noncollinear magnetic formalism and a newly introduced algorithm, we calculate the magnetic anisotropy barrier, whose value indicates the stability of the molecule’s magnetic moment.

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Section: Methodsmentioning

confidence: 99%

Magnetic Energy Landscape of Dimolybdenum Tetraacetate on a Bulk Insulator Surface

Cococcioni

Floris

2021

Applied Sciences

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“…In all these ab initio methods for computing U, key is the choice of the Hubbard projector functions. There are different types of Hubbard projectors [80], including nonorthogonalized atomic orbitals [34,[81][82][83], orthogonalized atomic orbitals [36,37,39,84], nonorthogonalized Wannier functions [85], orthogonalized Wannier functions [86], linearized augmented plane-wave approaches [87], and projector-augmented-wave projector functions [88,89]. It is well known that the values of the computed Hubbard U parameters strongly depend on the type of Hubbard projectors used [79,84].…”

Section: Introductionmentioning

confidence: 99%

Extensive Benchmarking of DFT+U Calculations for Predicting Band Gaps

et al. 2021

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Accurate computational predictions of band gaps are of practical importance to the modeling and development of semiconductor technologies, such as (opto)electronic devices and photoelectrochemical cells. Among available electronic-structure methods, density-functional theory (DFT) with the Hubbard U correction (DFT+U) applied to band edge states is a computationally tractable approach to improve the accuracy of band gap predictions beyond that of DFT calculations based on (semi)local functionals. At variance with DFT approximations, which are not intended to describe optical band gaps and other excited-state properties, DFT+U can be interpreted as an approximate spectral-potential method when U is determined by imposing the piecewise linearity of the total energy with respect to electronic occupations in the Hubbard manifold (thus removing self-interaction errors in this subspace), thereby providing a (heuristic) justification for using DFT+U to predict band gaps. However, it is still frequent in the literature to determine the Hubbard U parameters semiempirically by tuning their values to reproduce experimental band gaps, which ultimately alters the description of other total-energy characteristics. Here, we present an extensive assessment of DFT+U band gaps computed using self-consistent ab initioU parameters obtained from density-functional perturbation theory to impose the aforementioned piecewise linearity of the total energy. The study is carried out on 20 compounds containing transition-metal or p-block (group III-IV) elements, including oxides, nitrides, sulfides, oxynitrides, and oxysulfides. By comparing DFT+U results obtained using nonorthogonalized and orthogonalized atomic orbitals as Hubbard projectors, we find that the predicted band gaps are extremely sensitive to the type of projector functions and that the orthogonalized projectors give the most accurate band gaps, in satisfactory agreement with experimental data. This work demonstrates that DFT+U may serve as a useful method for high-throughput workflows that require reliable band gap predictions at moderate computational cost.

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“…In this Letter, we show calculations of e-ph interactions in the framework of DFT þ U, focusing on a prototypical Mott insulator, cobalt oxide (CoO), as a case study. While DFT predicts CoO to be a dynamically unstable metal, DFT þ U correctly predicts its antiferromagnetic insulating ground state [36,40]. We thus find that the long-range Fröhlich e-ph interaction is restored in DFPT þ U, and unphysical divergences of the e-ph coupling due to spurious soft modes are removed.…”

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confidence: 72%

“…It can predict the ground state of various families of correlated TMOs, including Mott insulators [23], high-temperature superconductors [32], and multiferroics [33,34]. Its linear response variant, DFPT þ U, has been employed successfully to study the lattice dynamics of TMOs [35][36][37][38]. As the Hubbard-U value can be computed ab initio [39], as we do here, the framework is entirely free of empirical parameters.…”

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confidence: 99%

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Ab Initio Electron-Phonon Interactions in Correlated Electron Systems

et al. 2021

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Electron-phonon (e-ph) interactions are pervasive in condensed matter, governing phenomena such as transport, superconductivity, charge-density waves, polarons, and metal-insulator transitions. Firstprinciples approaches enable accurate calculations of e-ph interactions in a wide range of solids. However, they remain an open challenge in correlated electron systems (CES), where density functional theory often fails to describe the ground state. Therefore reliable e-ph calculations remain out of reach for many transition metal oxides, high-temperature superconductors, Mott insulators, planetary materials, and multiferroics. Here we show first-principles calculations of e-ph interactions in CES, using the framework of Hubbard-corrected density functional theory (DFT þ U) and its linear response extension (DFPT þ U), which can describe the electronic structure and lattice dynamics of many CES. We showcase the accuracy of this approach for a prototypical Mott system, CoO, carrying out a detailed investigation of its e-ph interactions and electron spectral functions. While standard DFPT gives unphysically divergent and shortranged e-ph interactions, DFPT þ U is shown to remove the divergences and properly account for the longrange Fröhlich interaction, allowing us to model polaron effects in a Mott insulator. Our work establishes a broadly applicable and affordable approach for quantitative studies of e-ph interactions in CES, a novel theoretical tool to interpret experiments in this broad class of materials.

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Hubbard-corrected density functional perturbation theory with ultrasoft pseudopotentials

Cited by 56 publications

References 107 publications

Magnetic Energy Landscape of Dimolybdenum Tetraacetate on a Bulk Insulator Surface

Magnetic Energy Landscape of Dimolybdenum Tetraacetate on a Bulk Insulator Surface

Extensive Benchmarking of DFT+U Calculations for Predicting Band Gaps

Ab Initio Electron-Phonon Interactions in Correlated Electron Systems

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