Papers by Author: Alexey Bosak

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Authors: Maria Knjazeva, Yurii Bronwald, Daria Andronikova, Georgiy Lityagin, Alexey Bosak, Parisiadis Paraskevas, Krystian Roleder, Andrzej Majchrowski, Alexander Fotiadi, Alexey Filimonov, Roman G. Burkovsky
Abstract: Lead hafnate single crystals were characterized using single crystal x-ray diffraction under simultaneous application of hydrostatic pressure and high temperatures. The information on the structure of two intermediate phases, situated between antiferroelectric and paraelectric phases in the pressure-temperature phase diagram, has been obtained. The lower-temperature intermediate phase is characterized by incommensurate displacive modulations in Pb sublattice. The higher-temperature intermediate phase is characterized by oxygen framework distortion, primarily in the form of anti-phase tilts of the oxygen octahedra, which is also present in the lower-temperature intermediate phase.
Authors: Dieter Strauch, B. Dorner, A.A. Ivanov, M. Krisch, J. Serrano, Alexey Bosak, Wolfgang J. Choyke, B. Stojetz, Michael Malorny
Abstract: Preliminary results for the phonon dispersion curves of hexagonal 4H-SiC from experimental inelastic neutron (INS) and X-ray scattering (IXS) are reported and contrasted with those of cubic 3C-SiC and silicon. The experimental frequencies and scattering intensities are in excellent agreement with those from first-principles calculations using density-functional methods. The relative merits of the two experimental techniques and aspects of the density functional perturbation theory and the so-called frozen phonon method for the determination of the basic phonon properties are briefly outlined.
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