1,601 research outputs found
Some Low-Temperature Properties of a Generalized Hubbard Model with Correlated Hopping
In the present paper we study some correlation effects in a generalized
Hubbard model with correlated hopping within low-temperature region using a
generalized mean-field approximation. It is shown that in a series of cases the
model leads to consequences deviating essentially from those of the Hubbard
model. We consider the possibility of applying the result to interpret the
peculiarities of physical properties of systems with narrow energy bands.Comment: 2 pages, LaTex2e using Elsevier style, presented at LT22 Conference,
Helsinki, August 199
-electrons contribution to cohesive energy of -metals
In this paper a model for -subsystem of transition -metals has been
proposed and used for calculation of the cohesive energy dependent on -band
filling of particular metal, its bandwidth and effective intra-atomic
interaction value. It has been shown that the model enables one to explain the
observed peculiarities of cohesive energy effect on the atomic number. The
nature of two parabolic dependencies of cohesive energy on -band filling
has been clarified. The calculated values of cohesive energy are close to those
experimentally obtained for Sc-Ti-V-Cr-Mn-Fe series.Comment: 7 pages, 2 figures, 2 table
Phase Diagram of Metal-Insulator Transition in System with Anderson-Hubbard Centers
The model of a strongly correlated system in which periodically spaced
Anderson-Hubbard centers are introduced into narrow-band metal is considered.
Besides the interactions between localized magnetic moments and strong on-site
Coulomb interaction, the model takes into account the hybridization of
localized and band states. To study the efect of the lattice deformation on the
electrical properties of the system the phonon term and elastic energy have
been taken into account. Green functions for band and localized electrons have
been found. On this base, the energy spectrum has been investigated as function
of model parameters, temperature and external pressure. The criterion of
metal-insulator transition for integer value of electron concentration has been
derived and the phase diagram of the metal-insulator transition has been built.Comment: presented at 12 International Simposium on Physics of Materials,
Prague 4-8.09.201
Electron Correlations in Narrow Energy Bands: Ground State Energy and Metal-Insulator Transition
The electron correlations in narrow energy bands are examined in framework of
the Hubbard model. The single-particle Green function and energy spectrum are
obtained in paramagnetic state at half-filling by means of new two-pole
approximation. In the ground state analitical expressions for the energy gap,
polar states concentration and energy of the system are found. Metal-insulator
transitions in the model at change of bandwidth or temperature are
investigated. The obtained results are used for interpretation of some
experimental data in narrow-band materials.Comment: 12 pages, 11 eps figures, Latex 2.0
Pressure-Temperature Phase Diagram of Generalized Hubbard Model with Correlated Hopping at Half-Filling
In the present paper pressure-temperature phase diagram of a generalized
Hubbard model with correlated hopping in a paramagnetic state at half-filling
is determined by means of the generalized mean-field approximation in the Green
function technique. The constructed phase diagram describes metal-to-insulator
transition with increasing temperature, and insulator-to-metal transition under
the action of external pressure. The phase diagram can explain paramagnetic
region of the phase diagrams of some transition metal compounds. We have found
that taking into account correlated hopping allows much better description of
these experimental data than the Hubbard model; this testifies also much better
physics of the present model and the important role of correlated hopping.Comment: 7 pages, Latex 2.09 using Cond. Matt. Phys. style, submitted to
Condensed Matter Physic
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