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Information × Registration Number 0202U000221, 0199U000668 , R & D reports Title Investigation of phase transitions in bulk and spatially constrained statistical systems and microscopical description of their thermodynamic characteristics popup.stage_title Head Kozlovs'kyj Mykhajlo Pavlovych, Registration Date 24-01-2002 Organization Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine popup.description2 The report includes 108 pages of text. It consists of introduction, nine sections of main part, bibliography of 234 references. There are 33 figures and 13 tables in the report. Key words: phase transitions, anisotropic models, Ising model, XY model, reference system, spatially constrained systems, methods of numerical computations, thermodynamic characteristics Subjects of investigations: magnetic systems, ferroelectrics, liquid crystals, fluids, binary mixtures, disordered magnetic systems, magnetic systems with complicated symmetry, polymers, polymer networks, semi-infinite systems, d-dimensional latice systems. Task of work: Calulation of the properties of statistical systems near the phase transition points, application of the existing and development of the new methods for studying the critical behavior of a series of condensed systems, including those requiring the application of the effective Hamiltonians with the complicated symmetry for their theoretical description. Due to the universality o f critical phenomena the developed by us theory has different applications. We suggested a microscopic theory of the phase transition for three-dimensional lattice systems, which allows to establish the dependencies of the macroscopic characteristics of the system from microscopic parameters, to calculate the thermodynamic functions and order parameters (spontaneous polarization and magnetization) of the ferroelectric and ferromagnetic cluster systems in the neighborhood of the second-order phase transition points. The influence of the disorder on the critical properties of the diluted uniaxial magnets was considered, and the values of the effective critical exponents in such systems were obtained. Special features of the phase transition in three-dimensional systems with spherical and cubic symmetry were investigated. We have studied the scaling laws of the polymer macromolecules in the medium with long-range correlated defects. It was found that the scaling of polymers in such medium obeys the new laws. The properties of the diffusion-controlled reactions with absorbing states located on a polymer chain or a polymer star were were investigated. Numerical values of the exponents characterizing the reaction's velocity rate were obtained. Using the RG field-theoretical methods and the epsilon expansion, a complete study of the critical behavior in the neighborhood of the m-fold degenerate Lifshitz point was performed in the two-loop approximation. The influence of the weak bulk disorder on the surface critical behavior of semi-infinite systems at the ordinary and special phase transitions was studied, and the crossover phenomena between the above transitions was analysed. A calculation was performed of the critical temperature and the critical density of a model symmetric mixture of hard spheres interacting through the square well potential. The dependence of these values on the properties of the model, such as the depth of the well and the interaction range, was investigated. Product Description popup.authors popup.nrat_date 2020-04-02 Close