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Information × Registration Number 0299U001417, 0194U022986 , R & D reports Title Investigation of the effects, caused by the local anharmonicity and short-range interaction of the quantum fields of different nature, in the crystalline, disorbered and molecular systems popup.stage_title Head Stasyuk Igor Vasyl'ovych, Registration Date 24-09-1999 Organization Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine popup.description2 The instabilities of dieletric type and phase transitions between the states with different pseudospin orientation were investigated and the phase diagrams in regimes мю-=const and n=const were built. In the case of the constant electron concentration mean value the possibility of the appearance of the phase separated state was obtained. A criteria of the appearance of the ferroelectric and charge0ordered states was established for the YBaCuO-type structures/ The ingflyence of the vecancy random field was analyzed/ The seminumerical method of the reference account if anharmonicity was proposed for the locally anharmonic phonon models/ For the cases of the " 3+ 4" model and model with gaussian barrier the calculations of the ionic vibration spectrum, free energy and order parameters were performed, phase diagrams were built and the collective mode spestrum was investigated. An effective adiabatic ionic potentials for linear thr Cu-O-Cu type clusters in YBaCuO type structures and for hydrogen bonds wer e built within the frames of the electron-phonon model and on the basis of the quantum chemiccal calculations: the processes of electron in such objects were analyzed For superinic crystals with hydrogen bonds the model for protonic orderings was developed and on its basis the description of phase transitions between ferroelastic and superionic phases was given. An investigation of the protonuc contribution in conductivity in different phases was performrd for the crystals of M3H(XO4)2 (M=Rb, Cs, NH4; X=S, Se0 family within the Kubo theory with the use of the orientationnal-tunneling model of protonic transfer as reference. A consideration of the optical phenomena and and phase transitions caused by external field was performed for ferrorlectric crystals of KH2PO4 famil using the model of protonic ordering. The features of the Raman light scattering in the crystals with the phase transitions of order-disorder and Jahn-Teller type were analyzed. An investigation of the thermodynamical properties of one-d imensional pseudospin models ( spin-1/2 XY-chain) with Dzualoshinskii-Moriya interaction was perfomed. Onthe basis of the functional integral appriach the magnetic properties of the disordered s-d model were investigated. The methods of investigation of the transfer phenomena in the sustems of interacting bose particles was developed within the consistent description of kinetics and hydrodynamics scheme Product Description popup.authors popup.nrat_date 2020-04-03 Close