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Information × Registration Number 0213U002491, 0110U001377 , R & D reports Title Multiwave state modulated superstructure in dielectric crystals popup.stage_title Head Polovynko Igor, Registration Date 29-01-2013 Organization Ivan Franko National University of Lviv. Journalism Department popup.description2 Theoretically and experimentally studied the dynamics of the incommensurate modulation in dielectric crystals. It was found that the presence of incommensurate superstructure in the crystal there are three different phase transitions. Initial phase transition - incommensurate phase is a continuous phase transition of the second kind. Phase transition between the long-period commensurate phases may pass through an intermediate temperature interval of existence of chaotic phase. Phase transition between commensurate phases, provided that there is defect density waves in the temperature range of the existence of the block structure (similar to domain) regions with different wave vectors, and is characterized by the existence of the "old" and "new" phase. It is shown that in the incommensurate phase in the modulated superstructure is in the process of formation of wave spatial distribution of defects. When the defect density wave period coincides with the period of the modulated superstructure is a manifestation of their interaction is to increase the temperature range of the existence of a metastable state - the effect termooptichnoy memory. If the periods of these two waves of modulations do not match, but close to each other, because of their superposition is the formation of wave modulation with different values k = k1-k2, causes the abnormal behavior of the physical parameters. Found that in the transition temperature ranges occur chaotic phase, which is characterized by a change of the wave vector modulation inherent in the incommensurate phase, bounded by the two phases of the long-period commensurate with the point group symmetry, which are subgroups of the symmetry of the initial phase. In the chaotic phase, showed an increase in the coefficient of thermal conductivity, which is due to the contribution to the heat transfer of soft optical phonons. Product Description popup.authors Карпа Іван Васильович Катеринчук Іван Миколайович Рихлюк Сергій Вікторович Свелеба Сергій Андрійович popup.nrat_date 2020-04-02 Close