Computational modeling of actinide materials and complexes

In spite of being rare, actinide elements provide the building blocks for many fascinating condensed-matter systems, both from an experimental and theoretical perspective. Experimental observations of actinide materials are difficult because of rarity, toxicity, radioactivity, and even safety and security. Theory, on the other hand, has its own challenges. Complex crystal and electronic structures are often encountered in actinide materials, as well as pronounced electron correlation effects. Consequently, theoretical modeling of actinide materials and their 5f electronic states is very difficult. Here, we review recent theoretical efforts to describe and sometimes predict the behavior of actinide materials and complexes, such as phase stability including density functional theory (DFT), DFT in conjunction with an additional Coulomb repulsion U (DFT+U), and DFT in combination with dynamical mean-field theory (DFT+DMFT).

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Strong enhancement of magnetic order from bulk to stretched monolayer FeSe as Hund’s metals

npj Computational Materials ◽

10.1038/s41524-020-00414-3 ◽

2020 ◽

Vol 6 (1) ◽

Author(s):

Chang-Youn Moon

Keyword(s):

Density Functional ◽

Magnetic Order ◽

Mean Field Theory ◽

Mean Field ◽

Comprehensive Understanding ◽

Functional Theory ◽

Iron Based Superconductors ◽

Magnetic Orders ◽

Spatial Isolation ◽

Iron Based

Abstract Despite of the importance of magnetism in possible relation to other key properties in iron-based superconductors, its understanding is still far from complete especially for FeSe systems. On one hand, the origin of the absence of magnetic orders in bulk FeSe is yet to be clarified. On the other hand, it is still not clear how close monolayer FeSe on SrTiO3, with the highest transition temperature among iron-based superconductors, is to a magnetic instability. Here we investigate magnetic properties of bulk and monolayer FeSe using dynamical mean-field theory combined with density-functional theory. We find that suppressed magnetic order in bulk FeSe is associated with the reduction of interorbital charge fluctuations, an effect of Hund’s coupling, enhanced by a larger crystal-field splitting. Meanwhile, spatial isolation of Fe atoms in expanded monolayer FeSe leads into a strong magnetic order, which is completely destroyed by a small electron doping. Our work provides a comprehensive understanding of the magnetic order in iron-based superconductors and other general multi-orbital correlated systems as Hund’s metals.

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Magnetic Excitation Spectra inBaFe2As2: A Two-Particle Approach within a Combination of the Density Functional Theory and the Dynamical Mean-Field Theory Method

Physical Review Letters ◽

10.1103/physrevlett.107.137007 ◽

2011 ◽

Vol 107 (13) ◽

Cited By ~ 61

Author(s):

Hyowon Park ◽

Kristjan Haule ◽

Gabriel Kotliar

Keyword(s):

Density Functional ◽

Mean Field Theory ◽

Mean Field ◽

Dynamical Mean Field Theory ◽

Theory Method ◽

Excitation Spectra ◽

Functional Theory ◽

The Density Functional Theory ◽

Magnetic Excitation Spectra ◽

Particle Approach

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BEYOND DENSITY FUNCTIONAL THEORY: THE DOMESTICATION OF NONLOCAL POTENTIALS

Modern Physics Letters B ◽

10.1142/s021798490400669x ◽

2004 ◽

Vol 18 (02n03) ◽

pp. 73-82 ◽

Cited By ~ 7

Author(s):

ROBERT K. NESBET

Keyword(s):

Density Functional Theory ◽

Density Functional ◽

Correlation Energy ◽

Mean Field Theory ◽

Mean Field ◽

Energy Functional ◽

Functional Theory ◽

Large Molecules ◽

Cellular Method ◽

Nonlocal Potentials

Due to efficient scaling with electron number N, density functional theory (DFT) is widely used for studies of large molecules and solids. Restriction of an exact mean-field theory to local potential functions has recently been questioned. This review summarizes motivation for extending current DFT to include nonlocal one-electron potentials, and proposes methodology for implementation of the theory. The theoretical model, orbital functional theory (OFT), is shown to be exact in principle for the general N-electron problem. In practice it must depend on a parametrized correlation energy functional. Functionals are proposed suitable for short-range Coulomb-cusp correlation and for long-range polarization response correlation. A linearized variational cellular method (LVCM) is proposed as a common formalism for molecules and solids. Implementation of nonlocal potentials is reduced to independent calculations for each inequivalent atomic cell.

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Metal-Oxygen Hybridization and Core-Level Spectra in Actinide and Rare-Earth Oxides

MRS Advances ◽

10.1557/adv.2016.403 ◽

2016 ◽

Vol 1 (44) ◽

pp. 3007-3012 ◽

Cited By ~ 1

Author(s):

Jindřich Kolorenč

Keyword(s):

Rare Earth ◽

Density Functional ◽

Mean Field Theory ◽

Mean Field ◽

Core Level ◽

Dynamical Mean Field Theory ◽

Functional Theory ◽

The Core ◽

The Density Functional Theory ◽

Rare Earth Sesquioxides

ABSTRACT We employ a combination of the density-functional theory and the dynamical mean-field theory to study the electronic structure of selected rare-earth sesquioxides and dioxides. We concentrate on the core-level photoemission spectra, in particular, we illustrate how these spectra reflect the integer or fractional filling of the 4f orbitals. We compare the results to our earlier calculations of actinide dioxides and analyze why the core-level spectra of actinide compounds display a substantially reduced sensitivity to the filling of the 5f orbitals.

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Electron correlation effects in small iron clusters

Computing Letters ◽

10.1163/157404005776611484 ◽

2004 ◽

Vol 1 (4) ◽

pp. 288-296 ◽

Cited By ~ 18

Author(s):

G. Rollmann ◽

P. Entel

Keyword(s):

Electron Correlation ◽

Density Functional ◽

Magnetic Moments ◽

Coulomb Repulsion ◽

Correlation Effects ◽

Generalized Gradient ◽

Functional Theory ◽

Jahn Teller ◽

Electron Correlation Effects ◽

Ground State Structures

We present results of first-principles calculations of structural, magnetic, and electronic properties of small Fe clusters. It is shown that, while the lowest-energy isomers of Fe3 and Fe4 obtained in the framework of density functional theory within the generalized gradient approximation (GGA) are characterized by Jahn-Teller-like distortions away from the most regular shapes (which is in agreement with other works), these distortions are reduced when electron correlation effects are considered explicitly as within the GGA+U approach. At the same time, the magnetic moments of the clusters are enhanced with respect to the pure GGA case, resulting in maximal moments (in the sense of Hund’s rules) of 4 μB per atom for the ground state structures of Fe3 and Fe4, and a total moment of 18 μB for Fe5. This already happens for moderate values of the Coulomb repulsion parameter U̴ 2.0 eV and is explained by changes in the electronic structures of the clusters.

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Time-Dependent Density-Functional Theory Meets Dynamical Mean-Field Theory: Real-Time Dynamics for the 3D Hubbard Model

Physical Review Letters ◽

10.1103/physrevlett.106.116401 ◽

2011 ◽

Vol 106 (11) ◽

Cited By ~ 42

Author(s):

Daniel Karlsson ◽

Antonio Privitera ◽

Claudio Verdozzi

Keyword(s):

Field Theory ◽

Density Functional Theory ◽

Density Functional ◽

Mean Field Theory ◽

Mean Field ◽

Time Dependent ◽

Dynamical Mean Field Theory ◽

Functional Theory ◽

Time Dynamics ◽

Dependent Density

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Fock-Matrix Corrections in Density Functional Theory and Use in Embedded Mean-Field Theory

Journal of Chemical Theory and Computation ◽

10.1021/acs.jctc.6b00685 ◽

2016 ◽

Vol 12 (12) ◽

pp. 5811-5822 ◽

Cited By ~ 12

Author(s):

Kaito Miyamoto ◽

Thomas F. Miller ◽

Frederick R. Manby

Keyword(s):

Field Theory ◽

Density Functional Theory ◽

Density Functional ◽

Mean Field Theory ◽

Mean Field ◽

Functional Theory

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Influence of Molecular Orbitals on Magnetic Properties of FeO2Hx

Molecules ◽

10.3390/molecules25092211 ◽

2020 ◽

Vol 25 (9) ◽

pp. 2211 ◽

Cited By ~ 1

Author(s):

Alexey O. Shorikov ◽

Sergey L. Skornyakov ◽

Vladimir I. Anisimov ◽

Sergey V. Streltsov ◽

Alexander I. Poteryaev

Keyword(s):

Magnetic Properties ◽

Density Functional ◽

Mean Field Theory ◽

Mean Field ◽

Molecular Orbitals ◽

Metallic State ◽

Functional Theory ◽

High Pressure And Temperature ◽

Fe Ions ◽

Mass Enhancement

Recent discoveries of various novel iron oxides and hydrides, which become stable at very high pressure and temperature, are extremely important for geoscience. In this paper, we report the results of an investigation on the electronic structure and magnetic properties of the hydride FeO 2 H x , using density functional theory plus dynamical mean-field theory (DFT+DMFT) calculations. An increase in the hydrogen concentration resulted in the destruction of dimeric oxygen pairs and, hence, a specific band structure of FeO 2 with strongly hybridized Fe- t 2 g -O- p z anti-bonding molecular orbitals, which led to a metallic state with the Fe ions at nearly 3+. Increasing the H concentration resulted in effective mass enhancement growth which indicated an increase in the magnetic moment localization. The calculated static momentum-resolved spin susceptibility demonstrated that an incommensurate antiferromagnetic (AFM) order was expected for FeO 2 , whereas strong ferromagnetic (FM) fluctuations were observed for FeO 2 H.

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