1,464 research outputs found
Combining the Hybrid Functional Method with Dynamical Mean-Field Theory
We present a new method to compute the electronic structure of correlated
materials combining the hybrid functional method with the dynamical mean-field
theory. As a test example of the method we study cerium sesquioxide, a strongly
correlated Mott-band insulator. The hybrid functional part improves the
magnitude of the pd-band gap which is underestimated in the standard
approximations to density functional theory while the dynamical mean-field
theory part splits the 4f-electron spectra into a lower and an upper Hubbard
band.Comment: 5 pages, 2 figures, replaced with revised version, published in
Europhys. Let
Quantum nature of the critical points of substances
Thermodynamics of chemical elements, based on the two-component
electron-nuclear plasma model shows that the critical parameters for the
liquid-vapor transition are the quantum values for which the classical limit is
absent.Comment: 4 pages, no figure
Structural relaxation due to electronic correlations in the paramagnetic insulator KCuF3
A computational scheme for the investigation of complex materials with
strongly interacting electrons is formulated which is able to treat atomic
displacements, and hence structural relaxation, caused by electronic
correlations. It combines ab initio band structure and dynamical mean-field
theory and is implemented in terms of plane-wave pseudopotentials. The
equilibrium Jahn-Teller distortion and antiferro-orbital order found for
paramagnetic KCuF3 agree well with experiment.Comment: 4 pages, 3 figure
Computation of correlation-induced atomic displacements and structural transformations in paramagnetic KCuF3 and LaMnO3
We present a computational scheme for ab initio total-energy calculations of
materials with strongly interacting electrons using a plane-wave basis set. It
combines ab initio band structure and dynamical mean-field theory and is
implemented in terms of plane-wave pseudopotentials. The present approach
allows us to investigate complex materials with strongly interacting electrons
and is able to treat atomic displacements, and hence structural
transformations, caused by electronic correlations. Here it is employed to
investigate two prototypical Jahn-Teller materials, KCuF3 and LaMnO3, in their
paramagnetic phases. The computed equilibrium Jahn-Teller distortion and
antiferro-orbital order agree well with experiment, and the structural
optimization performed for paramagnetic KCuF3 yields the correct lattice
constant, equilibrium Jahn-Teller distortion and tetragonal compression of the
unit cell. Most importantly, the present approach is able to determine
correlation-induced structural transformations, equilibrium atomic positions
and lattice structure in both strongly and weakly correlated solids in their
paramagnetic phases as well as in phases with long-range magnetic order.Comment: 27 pages, 11 figure
The electronic structure of the heavy fermion metal
The electronic structure of the first reported heavy fermion compound without
f-electrons LiV_2O_4 was studied by an ab-initio calculation method. In the
result of the trigonal splitting and d-d Coulomb interaction one electron of
the configuration of V ion is localized and the rest partially fills
a relatively broad conduction band. The effective Anderson impurity model was
solved by Non-Crossing-Approximation method, leading to an estimation for the
single-site Kondo energy scale T_K. Then, we show how the so-called exhaustion
phenomenon of Nozi\`eres for the Kondo lattice leads to a remarkable decrease
of the heavy-fermion (or coherence) energy scale (D
is the typical bandwidth), comparable to the experimental result.Comment: 4 pages, RevTeX; 3 figures in format .eps. submitted to PR
Exchange interactions and magnetic properties of the layered vanadates CaV2O5, MgV2O5, CaV3O7 and CaV4O9
We have performed ab-initio calculations of exchange couplings in the layered
vanadates CaV2O5, MgV2O5, CaV3O7 and CaV4O9. The uniform susceptibility of the
Heisenberg model with these exchange couplings is then calculated by quantum
Monte Carlo method; it agrees well with the experimental measurements. Based on
our results we naturally explain the unusual magnetic properties of these
materials, especially the huge difference in spin gap between CaV2O5 and
MgV2O5, the unusual long range order in CaV3O7 and the "plaquette resonating
valence bond (RVB)" spin gap in CaV4O9
CrO2: a self-doped double exchange ferromagnet
Band structure calculations of CrO2 carried out in the LSDA+U approach reveal
a clear picture of the physics behind the metallic ferromagnetic properties.
Arguments are presented that the metallic ferromagnetic oxide CrO2 belongs to a
class of materials in which magnetic ordering exists due to double exchange (in
this respect CrO2 turns out to be similar to the CMR manganates). It is
concluded that CrO2 has small or even negative charge transfer gap which can
result in self-doping. Certain experiments to check the proposed picture are
suggested.Comment: 4 pages, 4 Figure
Electronic structure and effects of dynamical electron correlation in ferromagnetic bcc-Fe, fcc-Ni and antiferromagnetic NiO
LDA+DMFT method in the framework of the iterative perturbation theory (IPT)
with full LDA Hamiltonian without mapping onto the effective Wannier orbitals.
We then apply this LDA+DMFT method to ferromagnetic bcc-Fe and fcc-Ni as a test
of transition metal, and to antiferromagnetic NiO as an example of transition
metal oxide. In Fe and Ni, the width of occupied 3d bands is narrower than
those in LDA and Ni 6eV satellite appears. In NiO, the resultant electronic
structure is of charge-transfer insulator type and the band gap is 4.3eV. These
results are in good agreement with the experimental XPS. The configuration
mixing and dynamical correlation effects play a crucial role in these results
Electronic Structure and Lattice Relaxation Related to Fe in Mgo
The electronic structure of Fe impurity in MgO was calculated by the linear
muffin-tin orbital--full-potential method within the conventional local-density
approximation (LDA) and making use of the LDA+ formalism. The importance of
introducing different potentials, depending on the screened Coulomb integral
, is emphasized for obtaining a physically reasonable ground state of the
Fe ion configuration. The symmetry lowering of the ion electrostatic
field leads to the observed Jahn--Teller effect; related ligand relaxation
confined to tetragonal symmetry has been optimized based on the full-potential
total energy results. The electronic structure of the Fe ion is also
calculated and compared with that of Fe.Comment: 13 pages + 4 PostScript figures, Revtex 3.0, SISSA-CM-94-00
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