MEAN FIELD APPROACH TO THE GAP OF A MODEL INTERACTING SYSTEM

1988 ◽  
Vol 02 (01) ◽  
pp. 87-101
Author(s):  
KAJOLI BANERJEE ◽  
VIJAY A. SINGH ◽  
G. R. BHAT
Keyword(s):  
Density Functional ◽  
Local Density ◽  
Mean Field ◽  
Functional Theory ◽  
One Dimensional ◽  
Coulomb Term ◽  
The Density Functional Theory ◽  
The Mean ◽  
Transfer Term ◽  
Mean Field Approximations

The well-known local density approximation severely underestimates the gap of insulating materials. We undertake a study of an infinite one-dimensional model interacting system where the gap is known exactly. We use variational procedures, similar in spirit to Hohenberg and Kohn's derivation of the density functional theory. The mean field approximations so obtained are used to calculate the gap in the eigenspectrum. The gap is found to be systematically underestimated for realistic values of the parameters (u/t ≤ 4 where u is the Coulomb term and t, the transfer term). For u/t > 4, the approximate gap is in close agreement with the exact gap. The underestimation of the gap is investigated with respect to the discontinuity in the effective potential.

scholarly journals First-Principles Determination of the Polarizabilities of Carbon Tubules as a Function of Length

1994 ◽  
Vol 349 ◽  
Author(s):  
Andrew A. Quong ◽  
Mark R. Pederson
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Valence Electron ◽  
Local Density ◽  
Density Approximation ◽  
Functional Theory ◽  
Size Dependent ◽  
The Density Functional Theory ◽  
Linear And Nonlinear

ABSTRACTWe use the local-density-approximation to the density-functional theory to determine the axial polarizabilities of fullerene tubules as a function of length and winding topologies. Specifically, we present linear polarizabilities for tubules of composition C12H24, C36H24, C40H20 and C60H24. The size-dependent variation in the dipole-coupled gaps between pairs of occupied and unoccupied levels leads to enhancements in the polarizability per valence electron as the length of the tubule increases. The results are compared to recent densityfunctional based calculations of the linear and nonlinear polarizabilities for fullerene and benzene molecules.

FIRST-PRINCIPLES STUDIES ON THE ELECTRONIC STRUCTURE OF LuPd2Si2

2009 ◽  
Vol 23 (32) ◽  
pp. 5929-5934 ◽  
Author(s):  
T. JEONG
Keyword(s):  
Band Structure ◽  
First Principles ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Local Density ◽  
Spin Orbit Coupling ◽  
Electronic Band ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Structure Scheme

The electronic band structure of LuPd 2 Si 2 was studied based on the density functional theory within local density approximation and fully relativistic schemes. The Lu 4f states are completely filled and have flat bands around -5.0 eV. The fully relativistic band structure scheme shows that spin–orbit coupling splits the 4f states into two manifolds, the 4f7/2 and the 4f5/2 multiplet.

ELECTRONIC AND DYNAMICAL PROPERTIES OF MgB2 AND RELATED COMPOUNDS

2002 ◽  
Vol 16 (11n12) ◽  
pp. 1563-1569 ◽  
Author(s):  
G. PROFETA ◽  
A. CONTINENZA ◽  
F. BERNARDINI ◽  
G. SATTA ◽  
S. MASSIDDA
Keyword(s):  
Density Functional Theory ◽  
Local Density Approximation ◽  
Density Functional ◽  
Local Density ◽  
Density Approximation ◽  
Superconducting Properties ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Dynamical Properties ◽  
Related Compounds

We report a detailed study of the electronic and dynamical properties of MgB2 , BeB2 and of the AlMgB4 superlattice, within the local density approximation to the density functional theory. On the basis of our results we discuss the superconducting properties of these systems, and point to the high T c in MgB2 as a fortunate combination of events.

QUASILOCAL DENSITY FUNCTIONAL THEORY FOR NUCLEI INCLUDING PAIRING CORRELATIONS

2007 ◽  
Vol 16 (02) ◽  
pp. 249-262 ◽  
Author(s):  
X. VIÑAS ◽  
V. I. TSELYAEV ◽  
V. B. SOUBBOTIN ◽  
S. KREWALD
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Equations Of Motion ◽  
Mean Field ◽  
Field Operator ◽  
Functional Theory ◽  
Hartree Fock ◽  
Orbit Potential ◽  
The Density Functional Theory ◽  
Pairing Correlations

We propose first a generalization of the Density Functional Theory leading to single-particle equations of motion with a quasilocal mean-field operator containing a position-dependent effective mass and a spin-orbit potential. Ground-state properties of doubly magic nuclei are obtained within this framework using the Gogny D1S force and compared with the exact Hartree-Fock values. Next, extend the Density Functional Theory to include pairing correlations without formal violation of the particle-number condition. This theory, which is nonlocal, is simplified by a suitable quasilocal reduction. Some calculations to show the ability of this theory are presented.

Theoretical Study of Atoms Filled in Carbon Nanotubes

2016 ◽  
Vol 13 (10) ◽  
pp. 6974-6977
Author(s):  
Shuwen Cui ◽  
Weiwei Liu ◽  
Xiaosong Wang
Keyword(s):  
Carbon Nanotubes ◽  
First Principles ◽  
Density Functional ◽  
Theoretical Study ◽  
Local Density ◽  
First Principles Calculations ◽  
Functional Theory ◽  
One Dimensional ◽  
Local Density Functional Theory ◽  
Foreign Materials

The nano-sized quasi-one dimensional hollow cores of carbon nanotubes make it possible for them to be filled with and wetted by foreign materials. With C, S and Se atoms as example, we have studied the filling and wetting of these atoms into carbon nanotubes from local density functional theory in first principles calculations. The results suggest that the effect of nanotube length is negligible when it exceeds 3.6 Å, there is a relation between nanotube diameter and filling and wetting. Our studies would be important implications for the further use of carbon nanotubes.

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.

Quadrupole polarizabilities and Sternheimer antishielding factors in the density functional theory

1982 ◽  
Vol 60 (2) ◽  
pp. 210-221 ◽  
Author(s):  
M. J. Stott ◽  
E. Zaremba ◽  
D. Zobin
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Correlation Energy ◽  
Local Density ◽  
Closed Shell ◽  
Energy Functional ◽  
Functional Theory ◽  
Hartree Fock ◽  
Shielding Factor ◽  
The Density Functional Theory

The quadrupole polarizability and Sternheimer antishielding factor have been calculated for selected closed-shell atoms and ions using the density functional theory. In most cases, the results agree favourably with coupled Hartree–Fock calculations. However, for atoms with valence (d-shells the local density approximation used in the calculations is found to be inadequate. Our results suggest that refinements to the exchange-correlation energy functional are required in order to obtain accurate values for the polarizability and shielding factor of (d-shell atoms within a density functional approach.

scholarly journals PAIRING CORRELATIONS BEYOND THE MEAN FIELD

2007 ◽  
Vol 16 (02) ◽  
pp. 222-236 ◽  
Author(s):  
M. BENDER ◽  
T. DUGUET
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Mean Field ◽  
Energy Functional ◽  
Functional Theory ◽  
Self Consistent ◽  
Configuration Mixing ◽  
Pairing Correlations ◽  
The Mean

We discuss dynamical pairing correlations in the context of configuration mixing of projected self-consistent mean-field states, and the origin of a divergence that might appear when such calculations are done using an energy functional in the spirit of a naive generalized density functional theory.

Sign in / Sign up

Export Citation Format

Share Document