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Information × Registration Number 0202U000222, 0199U000670 , R & D reports Title Thermodynamics and kinetics of the pseudospin-fermion models of the locally-anharmonic crystalline and molecular systems with strong Hubbard correlations popup.stage_title Head Stasyuk I.V., Registration Date 01-02-2002 Organization Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine popup.description2 The report includes 244 pages of text. It consists of introduction, eleven sections of main part, conclusion, bibliography, the list of publications on the subject consisting of 98 references. There are 102 figures and 1 table in the report.Key words: Electron correlations, Hubbard model, local anharmonicity, pseudospin-electron model, thermodynamical parameters, phase transitions, high-temperature superconductors, hydrogen bond, ferroelectrics, superionic state, relativistic systems of particles.Subjects of investigations: high-temperature superconductors, ferroelectrics, superionic crystals and proton conductors, quantum and classical relativistic systems of interacting particles.Task of work was: to develop analytical approaches to the investigation of the hermodynamics, dynamics and kinetic properties of the crystalline and molecular systems with the strong short-range correlations of the fermi particles and local lattice anharmonicity; to describe theoretically the phase transitions and instabilit ies and to study the behaviour of the main thermodynamical and kinetic parameters in the region of such transformations.An approximate analytical schemes of the dynamical mean field theory for the strongly correlated electron systems (with the Hubbard's type interactions) are proposed and developed in the strong coupling case. The thermodynamically consistent procedure of calculation of the equilibrium values of physical quantities, correlation functions and modynamical potential is formulated for such systems; this approach is a complementation to the generalized random phase approximation. A method of the polarizability operator construction and the Raman scattering cross-section calculation is developed.The thermodynamic parameters are calculated and phase transitions are investigated in the pseudospin-electron model of the high-temperature superconducting (HTSC) systems in the cases of strong and weak coupling allowing for the possibility of appearance of the polar phase, modulated (including incommensura te) phase and the phase separation.Within the extended (so-called four-state) model of the phase transitions of the "order-disorder" type the description of bistability phenomena is given and the mechanism of the appearance of spatial inhomogeneities (of the phase separation type) is investigated in the oxygen subsystem of nonstoichiometric HTSC YBa2Cu3O7 ( in the presence of oxygen vacancies. Similar model is used at the investigation of thermodynamics of ferroelectric systems DMAAlS, DMAGaS having a reorientational mechanism of phase transitions.An investigation of the energy spectrum and thermodynamics of the quasi-one-dimensional proton conductors with chains of hydrogen bonds is performed; the explanation of pretransitional phenomena in the superionic transition region is given; the conditions of the dimerized phase appearance due to interaction with phonons are established. The effect of correlated proton-electron charge transfer along the hydrogen bond is investigated.The localization-delocalization t ransition in the proton subsystem of superionic crystal with hydrogen bonds is described; its connection with the structural relaxation processes is established. The coefficients of the proton conductivity are calculated; their temperature anomalies and frequency dispersion features in the vicinity of the superionic transition points are analyzed.It is performed an investigation of dynamic properties of semiquantum liquid at the consistent description of kinetics and hydrodynamics.With the application of quantum-chemical methods the adsorbtion process of the hydrogen and oxygen molecule and atoms as well as OH- groups on the transition metal surface is described; the equilibrium configuration of particles are determined; the effective distributions of electric charges are found.The classical and quantum relativistic systems of particles with the direct interaction are investigated. The relativistic two-particle spectra of bosons and fermions are found; the exclusion of the field degrees of freedom in the Hami lton description is performed; the radiation reaction forces are considered. Product Description popup.authors popup.nrat_date 2020-04-02 Close