http://dspace.nbuv.gov.ua:80/handle/123456789/32034 2026-04-20T05:39:24Z http://dspace.nbuv.gov.ua:80/handle/123456789/32051 Polar interface optical phonon states and their dispersive properties of a wurtzite GaN quantum dot: quantum size effect Zhang, L. Based on the macroscopic dielectric continuum model, the interface-optical-propagating (IO-PR) mixing phonon modes of a quasi-zero-dimensional (Q0D) wurtzite cylindrical quantum dot (QD) structure are derived and studied. The analytical phonon states of IO-PR mixing modes are given. It is found that there are two types of IO-PR mixing phonon modes, i.e. ρ-IO/z-PR mixing modes and the z-IO/ρ-PR mixing modes existing in Q0D wurtzite QDs. Each IO-PR mixing mode also has symmetrical and antisymmetrical forms. Via a standard procedure of field quantization, the Fröhlich Hamiltonians of electron-(IO-PR) mixing phonons interaction are obtained. The orthogonal relations of polarization eigenvectors for these IO-PR mixing modes are also displayed. Numerical calculations for a wurtzite GaN cylindrical QD are focused on the quantum size effect on the dispersive properties of IO-PR mixing modes. The results reveal that both the radial-direction size and the axial-direction size have great effect on the dispersive frequencies of the IO-PR mixing phonon modes. The limiting features of dispersive curves of these phonon modes are discussed in depth. The phonon modes "reducing" the behavior of wurtzite quantum confined structures have been explicitly observed in the systems. Moreover, the behaviors that the IO-PR mixing phonon modes in wurtzite Q0D QDs reduce to the IO modes and PR modes in wurtzite Q2D QW and Q1D QWR systems are profoundly analyzed both from the viewpoint of physics and mathematics. These results show that the present theories of polar mixing phonon modes in wurtzite cylindrical QDs are consistent with the phonon modes theories in wurtzite QWs and QWR systems. The analytical electron-phonon interaction Hamiltonians obtained here are useful in further analyzing the phonon effect on optoelectronic properties of wurtzite Q0D QD structures. 2010-01-01T00:00:00Z http://dspace.nbuv.gov.ua:80/handle/123456789/32050 Thermodynamics, dielectric permittivity and phase diagrams of the Rb1-x(NH4)xH2PO4 type proton glasses Sorokov, S.I.; Levitskii, R.R.; Vdovych, A.S. The cluster pseudospin model of proton glasses, which takes into account the energy levels of protons around the PO4 group, the long-range interactions between the hydrogen bonds, and an internal random deformational field is used to investigate thermodynamical characteristics, longitudinal and transverse dielectric permittivities of Rb1-x(ND4)xD2PO4 and Rb1-x(NH4)xH2AsO4 compounds. A review of experimental and theoretical works on the Rb1-x(NH4)xH2PO4 type crystals is presented. 2010-01-01T00:00:00Z http://dspace.nbuv.gov.ua:80/handle/123456789/32049 Dynamics of the Rochelle salt NaKC4H4O6·4H2O crystal studied within the Mitsui model extended by piezoelectric interaction and transverse field Levitskii, R.R.; Andrusyk, A.Ya.; Zachek, I.R. We calculated dynamic dielectric permittivity of the Rochelle salt within the Mitsui model, extended by piezoelectric interaction and transverse field. Calculations were based on the parameters derived earlier within the study of thermodynamic properties of Rochelle salt. The study of dynamic properties was performed within the Bloch equation method. We showed that taking transverse field into account allows for better description of the Rochelle salt relaxation dynamics. Furthermore, we showed that taking transverse field into account results in the appearance of a resonant component in dynamic permittivity like it is observed in experiment. However, in accordance with the calculations, resonant response reveals itself within infrared frequency range, whereas in experiment it is observed within submillimeter spectral region. 2010-01-01T00:00:00Z http://dspace.nbuv.gov.ua:80/handle/123456789/32048 Ferrimagnetism in the Hubbard, dimmer-connector frustrated chain Rössler, J.; Mainemer, D. We study the AB2 "dimmer-connector" chain within a generalized Hubbard model, which contains site-dependent parameters, and different chemical potentials for A and B sites. Considering one electron per atom, we carry out exact calculations for finite clusters, and derive some asymptotic results, valid for macroscopic chains. We take a non-vanishing intra-dimmer electron hopping, thus departing from the condition of a bipartite lattice. In spite of that, the system persists ferrimagnetic in some region of the parameter space, thus generalizing a theorem of Lieb for bipartite lattices. A somewhat surprising result is that the ferrimagnetic phase is possible, even for a very large chemical potential jump between A and B sites. In another respect, we show that a previously reported macroscopic (2N) degenerancy of the AB2 Heisenberg chain ground state (GS) is fully removed on going to the (more fundamental) Hubbard model, yielding a non-magnetic GS. 2010-01-01T00:00:00Z