Racah Materials: Role of Atomic Multiplets and Intermediate Valence in f-Electron Systems

MRS Advances ◽  
2016 ◽  
Vol 1 (44) ◽  
pp. 2967-2974 ◽  
Author(s):  
A. I. Lichtenstein ◽  
J. Kolorenc ◽  
A. B. Shick ◽  
M. I. Katsnelson
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Ground State ◽  
Density Functional ◽  
Singlet Ground State ◽  
Intermediate Valence ◽  
Kondo Insulator ◽  
The Density Functional Theory ◽  
Indirect Band Gap ◽  
The Moment

ABSTRACT The electronic structure of PuB6, an actinide analog of SmB6 , was investigated making use of a combination of the density functional theory (DFT), and the exact diagonalization (ED) of an effective discrete Anderson impurity model. Intermediate valence ground state with the f-shell occupation n4f =5.5 for the Pu atom in PuB6 is calculated. The 5f-shell magnetic moment is completely compensated by the moment carried by the electrons in the conduction band. Already in DFT, PuB6 is an insulator with a small amount of holes near the X-point, and the indirect band gap of ≈60 meV. This band gap becomes direct in DFT+ED calculations supporting the idea of “topological Kondo insulator” in PuB6. Connection between the electronic structure of PuB6 and δ-Pu is established. We propose that these materials belong to a new class of intermediate valence “Racah” materials with the multi-orbital “Kondo-like” singlet ground-state.

scholarly journals Electronic structure, elasticity, Debye temperature and anisotropy of cubic WO 3 from first-principles calculation

2018 ◽  
Vol 5 (6) ◽  
pp. 171921 ◽  
Author(s):  
Xing Liu ◽  
Hui-Qing Fan
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Debye Temperature ◽  
Density Functional ◽  
Elastic Wave Velocity ◽  
Point Of View ◽  
First Principles Calculation ◽  
Shear Moduli ◽  
Charge Densities ◽  
Indirect Band Gap

The electron structure, elastic constant, Debye temperature and anisotropy of elastic wave velocity for cubic WO 3 are studied using CASTEP based on density functional theory. The optimized structure is consistent with previous work and the band gap is obtained by computing the electronic structure; the top of the valence band is not at the same point as the bottom of the conduction band, which is an indirect band-gap oxide. Electronic properties are studied from the calculation of band structure, densities of states and charge densities. The bulk and shear moduli, Young's modulus, hardness and Poisson's ratio for WO 3 are studied by the elastic constants. We calculated acoustic wave velocities in different directions and estimated the Debye temperature from the acoustic velocity. The anisotropy of WO 3 was analysed from the point of view of a pure wave and quasi wave.

First-principle study of the electronic structure and optical property of Nb-doped anatase TiO2

2014 ◽  
Vol 28 (17) ◽  
pp. 1450091
Author(s):  
Q. Y. Hou ◽  
Q. L. Liu ◽  
C. W. Zhao ◽  
Y. Zhang
Keyword(s):  
Electronic Structure ◽  
Optical Property ◽  
Band Gap ◽  
Absorption Edge ◽  
Short Wavelength ◽  
Density Functional ◽  
Functional Theory ◽  
Long Wavelength ◽  
The Density Functional Theory ◽  
The Stability

The absorption edge shifted to long wavelength direction and short wavelength direction of two opposite experimental conclusions have been reported, when the band-gap and absorption spectra of Nb -doped anatase TiO 2 were studied. In order to solve this contradiction, the electronic structure and the optical property of Nb heavy doped anatase TiO 2 have been studied by the first-principles plane-wave ultrasoft pseudopotential method based on the density functional theory with +U method modification. The calculated results indicate that the higher the Nb -doping is, the higher the total energy is, the worse the stability is, the higher the formation energy is, the more difficult the doping is, the wider the optical band-gap is, the more obvious the absorption edge shifting to short wavelength direction is, the lower the absorptivity and the reflectivity is, which is in agreement with the experimental results. The reasonable interpretation of the contradiction has been reported in this paper, too.

Strain-tunable electronic structure of two-dimensional monolayer SiP

2021 ◽  
pp. 2150404
Author(s):  
Xiao Han ◽  
Fan-Shun Meng ◽  
Xiao-Jie Yan ◽  
Hui Zhang
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Honeycomb Lattice ◽  
Application Range ◽  
Direct Band Gap ◽  
Direct Band ◽  
Indirect Band Gap ◽  
Armchair Direction

The 2D monolayer [Formula: see text]-SiP has a honeycomb lattice and an intrinsic indirect band gap. Herein, the density functional theory calculations are performed to modulate the electronic structure of 2D monolayer [Formula: see text]-SiP by applying strains. The band gap of monolayer [Formula: see text]-SiP is monotonously reduced by the strains. More interestingly, a direct band gap is more likely to be achieved by applying strains along the armchair direction than along the zigzag direction. Finally, 2D monolayer [Formula: see text]-SiP can possess a tunable direct band gap of 1.57–0.73 eV (HSE06) and considerable visible light absorption index, by applying compression strains of −6–−10% along the armchair direction. The work provides a route of modulating the electronic and optical properties of monolayer [Formula: see text]-SiP, which extends its application range for various fields such as electronic devices and solar energy conversion.

First Principle Study of the Electronic Structure of Gd2SrAl2O7

2010 ◽  
Vol 434-435 ◽  
pp. 448-450
Author(s):  
J. Feng ◽  
Wei Pan ◽  
B. Xiao ◽  
Rui Fen Wu ◽  
Chun Lei Wan ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Ground State ◽  
First Principles ◽  
Density Functional ◽  
First Principle ◽  
Ionic Bond ◽  
Covalent Character ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
A Charge

The ground state electronic structure of Gd2SrAl2O7 are calculated using first principles, we found that only the Density functional theory (DFT) + U can correctly describe the Gd2SrAl2O7 as a charge-transfer type insulator. Gd-O and Al-O bonds have strong covalent character and Sr-O is a perfect ionic bond. The band gap of Gd2SrAl2O7is 3.9 eV, and it is opened due the large U correction for 4f orbit.

First-Principles Study on Electronic Structure of 15R-SiC Polytypes

2014 ◽  
Vol 971-973 ◽  
pp. 77-80 ◽  
Author(s):  
Fu Chun Zhang ◽  
Ying Gao ◽  
Hong Wei Cui ◽  
Xing Xiang Ruan ◽  
Wei Hu Zhang
Keyword(s):  
Electronic Structure ◽  
Band Structure ◽  
Charge Density ◽  
Band Gap ◽  
Density Functional ◽  
Covalent Bond ◽  
Lattice Parameter ◽  
Pseudopotential Approach ◽  
Structure Density ◽  
Indirect Band Gap

To study the geometrical and electronic structure of 15R-SiC polytypes, the lattice parameter, band structure, density of states (DOS) and charge density of 15R-SiC are calculated by using density functional theory based on the plane wave pseudopotential approach, and electronic structure and ground properties of 15R-SiC are investigated by the calculated band structure and DOS, the results show that 15R-SiC is an indirect band gap semiconductor, with calculated indirect band gap width being 2.16 eV and band gap dependent on Si 3p and C 2p states. While charge density results show that Si-C bond is a hybrid bond semiconductor strong in covalent bond and weak in ionicity, characterized by intense sp3 hybrid characteristics, which is in accordance with the experimental results. The above mentioned results are considered as theoretical reference for design and application of SiC polytype materials.

Electronic Structure and Ground State Properties of A4[Ag4O4] (A=Na, K and Rb): A First-Principles Study

2013 ◽  
Vol 665 ◽  
pp. 43-48
Author(s):  
Rajagopalan Umamaheswari ◽  
M. Yogeswari ◽  
G. Kalpana
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Ground State ◽  
First Principles ◽  
Density Functional ◽  
Electronic Band Structure ◽  
First Principles Calculation ◽  
Partial Density ◽  
Electronic Band ◽  
Ground State Properties

The first-principles calculation within density functional theory is used to study in detail the electronic structure and ground state properties of alkali-metal oxoargenates A4[Ag4O4] (A= Na, K and Rb). The total energies calculated within the atomic sphere approximation (ASA) were used to determine the ground state properties such as equilibrium lattice parameter, c/a ratio, bulk modulus and cohesive energy. The theoretically calculated equilibrium lattice constants values are in well agreement with the available experimental values. The electronic band structures, total and partial density of states are calculated. The result of electronic band structure shows that the KAgO and RbAgO are direct band gap semiconductors with their gap lying between the Γ-Γ points, whereas NaAgO is found to be an indirect band gap semiconductor with its gap lying between Z-Γ points.

Electronic structure and magnetic ordering in gadolinium-doped AlGaN from LSDA + U calculations

2018 ◽  
Vol 07 (03) ◽  
pp. 1850019 ◽  
Author(s):  
S. Belhachi ◽  
S. Amari ◽  
B. Bouhafs
Keyword(s):  
Density Functional Theory ◽  
Magnetic Properties ◽  
Band Gap ◽  
First Principles ◽  
Density Functional ◽  
Magnetic Ordering ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Indirect Band Gap

We present first-principles calculations of the structural, electronic and magnetic properties of Gd-doped [Formula: see text] based on the density functional theory within [Formula: see text] schemes. It is found that Gd atom favors substituting for Al site. Compared with undoped [Formula: see text], the Gd-doped [Formula: see text] has become an indirect band gap semiconductor of reduced band gap. The magnetic moment [Formula: see text] per molecule mainly comes from Gd ion with little contribution from the Ga, Al and N atoms. It is confirmed that the ferromagnetic configuration is stable for [Formula: see text]. It is found also that there is hybridization between the forbital of the Gd atom and the [Formula: see text] orbital of the N atom.

Adsorption of Sulfur’s Atoms on the Outer Surface of Carbon Nanotubes

2015 ◽  
Vol 1091 ◽  
pp. 25-29
Author(s):  
Sergey Anatolevich Sozykin ◽  
Valeriy Petrovich Beskachko
Keyword(s):  
Carbon Nanotubes ◽  
Ground State ◽  
Density Functional ◽  
Periodic Boundary Conditions ◽  
Chemical Bonds ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
The Moment ◽  
Ribbon Structures ◽  
Slight Deformation

The article is about regularities of structure formation of carbon nanotubes (7,7) in their ground state in the process of the gradually increasing of the concentration of sulfur atoms. The fragment of nanotube is investigated within the framework of the density functional theory with the using of periodic boundary conditions. It contains 112 carbon atoms and n = 1 ÷ 9 sulfur atoms. It is shown that the most energetically favorable configurations of n = 1 ÷ 6 sulfur atoms can be considered as a configuration uncombined sulfur clusters Sn with the slight deformation by tube field. From n = 6, there is a tendency toward the formation of a ribbon structures with 2 sulfur atoms wide, it has a tendency in the moment of increasing n to be guided by transversely to the tube axis. In all considered cases the sulfur atoms are located at a distance from the surface of the tube more than 0.28 nm, it is excluded the possibility of the formation of the strong (covalent) chemical bonds with the carbon nanotube.

The Density Functional Study of Electronic Properties for Bismuth Aluminate

2013 ◽  
Vol 873 ◽  
pp. 877-882
Author(s):  
Lian Wei Shan ◽  
Wei Li ◽  
Rui Fang ◽  
Li Min Dong ◽  
Zhi Dong Han ◽  
...  
Keyword(s):  
Band Gap ◽  
Conduction Band ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Functional Study ◽  
Functional Theory ◽  
Interaction Range ◽  
Plane Wave Method ◽  
The Density Functional Theory ◽  
Indirect Band Gap

In this paper, the density functional theory calculations on the electronic structure of BiAlO3 by using ultrasoft pseudopotential plane wave method are carried out. The results show that cubic and trigonal BiAlO3 are indirect band gap semiconductor. And their conduction band is 0.70 and 1.49 eV, respectively. The broadening antibonding interaction range in conduction band is found. It is largely responsible for the decrease in the band gap of cubic BiAlO3. It can be also found that the CB width is obviously narrowed, while the VB width is slightly broadened.

A comparison study of the structural electronic, elastic and lattice dynamic properties of ZrInAu and ZrSnPt

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sinem Erden Gulebaglan ◽  
Emel Kilit Dogan
Keyword(s):  
Bulk Modulus ◽  
Band Gap ◽  
Density Functional ◽  
Dynamic Properties ◽  
Elastic Stiffness ◽  
Functional Theory ◽  
Density Functional Perturbation Theory ◽  
The Density Functional Theory ◽  
Indirect Band Gap ◽  
First Time

Abstract To estimate the structural, electronic, elastic and dynamic properties of ZrInAu and ZrSnPt compounds, the density functional theory within the general gradient approximation was used. The computed lattice parameters, bulk modulus and the derivation of bulk modulus with respect to pressure were displayed and compared with the theoretical result. The indirect band gap for ZrInAu was found to be 0.48 eV, and for ZrSnPt the indirect band gap was found as 1.01 eV. Elastic stiffness constants, bulk, shear and Young’s module, Poisson’s coefficients and Zener anisotropy factor are calculated. Elastic properties showed that the ZrSnPt compound is more durable than the ZrInAu compound. Phonon distribution curves and density of states were investigated using a density functional perturbation theory. Both ZrInAu and ZrSnPt compounds were demonstrated to be dynamically stable. The results of this study were obtained for the first time in the literature. These results will make an important contribution to the literature.

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