198 research outputs found
Analytic continuation-free Green's function approach to correlated electronic structure calculations
We present a new charge self-consistent scheme combining Density Functional
and Dynamical Mean Field Theory, which uses Green's function of multiple
scattering-type. In this implementation the many-body effects are incorporated
into the Kohn-Sham iterative scheme without the need for the numerically
ill-posed analytic continuation of the Green's function and of the self-energy.
This is achieved by producing the Kohn-Sham Hamiltonian in the sub-space of
correlated partial waves and allows to formulate the Green's function directly
on the Matsubara axis. The spectral moments of the Matsubara Green's function
enable us to put together the real space charge density, therefore the charge
self-consistency can be achieved. Our results for the spectral functions
(density of states) and equation of state curves for transition metal elements,
Fe, Ni and FeAl compound agree very well with those of Hamiltonian based
LDA+DMFT implementations. The current implementation improves on numerical
accuracy, requires a minimal effort besides the multiple scattering formulation
and can be generalized in several ways that are interesting for applications to
real materials
Typical-medium, multiple-scattering theory for disordered systems with Anderson localization
The typical medium dynamical cluster approximation (TMDCA) is reformulated in
the language of multiple scattering theory to make possible first principles
calculations of the electronic structure of substitutionally disordered alloys
including the effect of Anderson localization. The TMDCA allows for a
systematic inclusion of non-local multi-site correlations and at same time
provides an order parameter, the typical density of states, for the Anderson
localization transition. The relation between the dynamical cluster
approximation and the multiple scattering theory is analyzed, and is
illustrated for a tight-binding model.Comment: 15 pages, 11 figure
Rare-earth impurities in CoMnSi: an opportunity to improve Half-Metallicity at finite temperatures
We analyse the effects of doping Holmium impurities into the full-Heusler
ferromagnetic alloy CoMnSi. Experimental results, as well as theoretical
calculations within Density Functional Theory in the "Local Density
Approximation plus Hubbard U" framework show that the holmium moment is aligned
antiparallely to that of the transition metal atoms. According to the
electronic structure calculations, substituting Ho on Co sites introduces a
finite density of states in the minority spin gap, while substitution on the Mn
sites preserves the half-metallic character.Comment: 22 pages, 8 figures. published in PR
Static corrections versus dynamic correlation effects in the valence band Compton profile spectra of Ni
We compute the Compton profile of Ni using the Local Density Approximation of
Density Functional Theory supplemented with electronic correlations treated at
different levels. The total/magnetic Compton profiles show not only
quantitative but also qualitative significant differences depending weather
Hubbard corrections are treated at a mean field +U or in a more sophisticated
dynamic way. Our aim is to discuss the range and capability of electronic
correlations to modify the kinetic energy along specific spatial directions.
The second and the fourth order moments of the difference in the Compton
profiles are discussed as a function of the strength of local Coulomb
interaction .Comment: 10 pages, 7 figs., submitted to PR
Scaling behavior of the momentum distribution of a quantum Coulomb system in a confining potential
We calculate the single-particle momentum distribution of a quantum
many-particle system in the presence of the Coulomb interaction and a confining
potential. The region of intermediate momenta, where the confining potential
dominates, marks a crossover from a Gaussian distribution valid at low momenta
to a power-law behavior valid at high momenta. We show that for all momenta the
momentum distribution can be parametrized by a -Gaussian distribution whose
parameters are specified by the confining potential. Furthermore, we find that
the functional form of the probability of transitions between the confined
ground state and the excited state is invariant under scaling of the
ratio , where is the transferred momentum and is the
corresponding excitation energy. Using the scaling variable the
maxima of the transition probabilities can also be expressed in terms of a
-Gaussian.Comment: 6 pages, 5 figure
Multiple scattering formalism for correlated systems: A KKR+DMFT approach
We present a charge and self-energy self-consistent computational scheme for
correlated systems based on the Korringa-Kohn-Rostoker (KKR) multiple
scattering theory with the many-body effects described by the means of
dynamical mean field theory (DMFT). The corresponding local multi-orbital and
energy dependent self-energy is included into the set of radial differential
equations for the single-site wave functions. The KKR Green's function is
written in terms of the multiple scattering path operator, the later one being
evaluated using the single-site solution for the -matrix that in turn is
determined by the wave functions. An appealing feature of this approach is that
it allows to consider local quantum and disorder fluctuations on the same
footing. Within the Coherent Potential Approximation (CPA) the correlated atoms
are placed into a combined effective medium determined by the dynamical mean
field theory (DMFT) self-consistency condition. Results of corresponding
calculations for pure Fe, Ni and FeNi alloys are presented.Comment: 25 pages, 5 fig. acepted PR
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