scholarly journals Electronic and Transport Properties of Sr-site Substituted: CaxSr(1-x)VO3

2021 ◽  
Vol 7 (1) ◽  
pp. 6-17
Author(s):  
R. K. Rai ◽  
R. B. Ray ◽  
G. C. Kaphle ◽  
O. P. Niraula
Keyword(s):  
Phase Transition ◽  
Density Functional ◽  
Chemical Potential ◽  
Mean Field Theory ◽  
Mean Field ◽  
Strongly Correlated ◽  
Entropy Model ◽  
Functional Theory ◽  
Insulator Phase Transition ◽  
Transition Behaviour

The Mott-insulator phase transition behaviour of the superstructure of strongly correlated system, CaxSr(1-x)VO3 (x =0, 0.33, 0.67, 1) have studied using the conventional density functional theory and the dynamical mean field theory. The Mott-Hubbard metal-insulator phase transition of superstructures, Ca0.33Sr0.67VO3 and Ca0.67Sr0.33VO3 formed by the CaVO3 and SrVO3 correlated metals, are obtained at U=4.5eV with β= 6(eV)-1 and U =4.5eV with β= 7(eV)-1 respectively. The values of U and β calculated through the Maximum Entropy model using the Green’s function data, are consistent with the experimental results. The value of Seebeck coefficient (S) of superstructure Ca0.33Sr0.67VO3 and Ca0.67Sr0.33VO3 are found to be +0.0011[V/K] and -0.0011[V/K] within the chemical potential  μ = -1.266 eV to μ = -0.938 eV. The figures of merit (ZT) are found to be 0.97 at room temperature for these systems. The variation of electrical and thermal conductivities has also been discussed.

scholarly journals Electronic Structure and Transport Properties of Superlattices: La(1-X)SrxTiO3 (X =0, 0.20, 0.80, 1)

2020 ◽  
Vol 6 (2) ◽  
pp. 134-148
Author(s):  
R. K. Rai ◽  
G. C. Kaphle ◽  
R. B. Ray ◽  
O. P. Niraula
Keyword(s):  
Field Theory ◽  
Phase Transition ◽  
Figure Of Merit ◽  
Density Functional ◽  
Chemical Potential ◽  
Mean Field Theory ◽  
Mean Field ◽  
Dynamical Mean Field Theory ◽  
Functional Theory ◽  
Metal Insulator

The conventional density functional theory (DFT) and dynamical mean field theory (DMFT) is used to study the structural, electronic and the Mott-Hubbard metal-insulator phase transition of the pristine and superstructures, La(1-x)SrxTiO3 (x = 0, 0.20, 0.80, 1). The electrical and thermal conductivities, Seebeck coefficient, Figure of merit are calculated using the BoltzTraP codes. The present study reveals that the direct band gap of 2.20 eV and indirect band gap ~2.0 eV at the Γ point in the Brillouin zone of SrTiO3 is upgraded to 3.423eV by using modified Beck-Johnson (mBJ) interaction potential. The metal-insulator transition (MIT) of LaTiO3 and the superlattice La(1-x)SrxTiO3 have been investigated by using conventional density functional theory (DFT) and dynamical mean field theory (DMFT). The Mott-Hubbard metal-insulator transitions for pristine LaTiO3 for a Coulombian parameter, U = 2.5 eV and the thermodynamic parameter β = 6 (eV)-1 are consistent with the experimental results. A typical set of these correlation parameters for MIT La0.20Sr0.80TiO3 and La0.80Sr0.20TiO3 systems are found to be U = 3.5 eV and β = 10(eV)-1 and U = 3.2 eV and β = 10 (eV)-1 respectively. The characteristic sharp quasi-particle peak for a sample of La0.80Sr0.20TiO3 superlattice systems is obtained correlation parameter U = 3.0 eV and β = 6(eV)-1. A thermoelectric phase transition is observed for Seebeck Coefficient at temperature 300 K at near chemical potential, μ = 1eV of SrTiO3. The corresponding figure of merit (ZT) with chemical potential (μ) appears to be unity at near μ = 1eV.

scholarly journals Thermoelectric properties plus phonon and de Haas–van Alphen frequencies of hole/electron-doped $$\hbox {CeIn}_3$$

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
M. Yazdani-Kachoei ◽  
S. Rahimi ◽  
R. Ebrahimi-Jaberi ◽  
J. Nematollahi ◽  
S. Jalali-Asadabadi
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Power Factor ◽  
Figure Of Merit ◽  
Density Functional ◽  
Kondo Effect ◽  
Mean Field Theory ◽  
Mean Field ◽  
Functional Theory

AbstractWe investigate temperature, pressure, and localization dependence of thermoelectric properties, phonon and de Haas–van Alphen (dHvA) frequencies of the anti-ferromagnetic (AFM) CeIn$$_3$$ 3 using density functional theory (DFT) and local, hybrid, and band correlated functionals. It is found that the maximum values of thermopower, power factor, and electronic figure of merit of this compound occur at low (high) temperatures provided that the 4f-Ce electrons are (not) localized enough. The maximum values of the thermopower, power factor, electronic figure of merit (conductivity parameters), and their related doping levels (do not) considerably depend on the localization degree and pressure. The effects of pressure on these parameters substantially depend on the degree of localization. The phonon frequencies are calculated to be real which shows that the crystal is dynamically stable. From the phonon band structure, the thermal conductivity is predicted to be homogeneous. This prediction is found consistent with the thermal conductivity components calculated along three Cartesian directions. In analogous to the thermoelectric properties, it is found that the dHvA frequencies also depend on both pressure and localization degree. To ensure that the phase transition at Néel temperature cannot remarkably affect the results, we verify the density of states (DOS) of the compound at the paramagnetic phase constructing a non-collinear magnetic structure where the angles of the spins are determined so that the resultant magnetic moment vanishes. The non-collinear results reveal that the DOS and whence the thermoelectric properties of the compound are not changed considerably by the phase transition. To validate the accuracy of the results, the total and partial DOSs are recalculated using DFT plus dynamical mean-field theory (DFT+DMFT). The DFT+DMFT DOSs, in agreement with the hybrid DOSs, predict the Kondo effect in this compound.

scholarly journals Structural properties of hypothetical CeBa2Cu3O7 compound from LSDA+DMFT calculations

2016 ◽  
Vol 34 (3) ◽  
pp. 617-626 ◽  
Author(s):  
Maciej Łuszczek
Keyword(s):  
Density Functional ◽  
Electronic Band Structure ◽  
Mean Field Theory ◽  
Mean Field ◽  
Local Spin Density Approximation ◽  
Strongly Correlated ◽  
Electronic Band ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Induced Changes

AbstractThe hypothetical stoichiometric CeBa2Cu3O7 (Ce123) compound, which has not been synthesized as a single phase yet, was studied by the density functional theory (DFT). We utilized a method which merges the local spin density approximation (LSDA) with the dynamical mean-field theory (DMFT) to account for the electronic correlations. The LSDA+DMFT calculations were performed in the high-temperature range. The particular emphasis was put on the pressure-induced changes in the electronic band structure related to strongly correlated 4f states. The computational results indicate the occurrence of a large negative volumetric thermal expansion coefficient near T = 500 K and a trace of a low-volume isostructural metastable state at high temperatures.

Nature of Non-magnetic Strongly-Correlated State in Plutonium

2006 ◽  
Vol 986 ◽  
Author(s):  
Leniod Purovskii ◽  
Alexander Shick ◽  
Ladislav Havela ◽  
Mikhail Katsnelson ◽  
Alexander Lichtenstein
Keyword(s):  
Field Theory ◽  
Density Functional ◽  
Local Density ◽  
Mean Field Theory ◽  
Mean Field ◽  
Dynamical Mean Field Theory ◽  
Cubic Phase ◽  
Face Centered Cubic ◽  
Strongly Correlated ◽  
Starting Point

AbstractLocal density approximation for the electronic structure calculations has been highly successful for non-correlated systems. The LDA scheme quite often failed for strongly correlated materials containing transition metals and rare-earth elements with complicated charge, spin and orbital ordering. Dynamical mean field theory in combination with the first-principle scheme (LDA+DMFT) can be a starting point to go beyond static density functional approximation and include effects of charge, spin and orbital fluctuations. Ab-initio relativistic dynamical mean-field theory is applied to resolve the long-standing controversy between theory and experiment in the “simple” face-centered cubic phase of plutonium called δ-Pu. In agreement with experiment, neither static nor dynamical magnetic moments are predicted. In addition, the quasiparticle density of states reproduces not only the peak close to the Fermi level, which explains the large coefficient of electronic specific heat, but also main 5f features observed in photoelectron spectroscopy.

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

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.

scholarly journals BEYOND DENSITY FUNCTIONAL THEORY: THE DOMESTICATION OF NONLOCAL POTENTIALS

2004 ◽  
Vol 18 (02n03) ◽  
pp. 73-82 ◽  
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.

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

MRS Advances ◽  
2016 ◽  
Vol 1 (44) ◽  
pp. 3007-3012 ◽  
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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