Browsing by Subject "Structural transformation"

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    Direct evidence for the instability and deactivation of mixed-oxide systems: influence of surface segregation and subsurface diffusion
    (2011) Emmez, E.; Vovk, E. I.; Bukhtiyarov V. I.; Ozensoy, E.
    In the current contribution, we provide a direct demonstration of the thermally induced surface structural transformations of an alkaline-earth oxide/transition metal oxide interface that is detrimental to the essential catalytic functionality of such mixed-oxide systems toward particular reactants. The BaOx/TiO2/Pt(111) surface was chosen as a model interfacial system where the enrichment of the surface elemental composition with Ti atoms and the facile diffusion of Ba atoms into the underlying TiO2 matrix within 523 873 K leads to the formation of perovskite type surface species (BaTiO3/Ba2TiO4/BaxTiyOz). At elevated temperatures (T > 973 K), excessive surface segregation of Ti atoms results in an exclusively TiO2/TiOx-terminated surface which is almost free of Ba species. Although the freshly prepared BaOx/TiO2/Pt(111) surface can strongly adsorb ubiquitous catalytic adsorbates such as NO2 and CO2, a thermally deactivated surface at T > 973 K practically loses all of its NO2/CO2 adsorption capacity due to the deficiency of surface BaOx domains.
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    Quantum bistability, structural transformation, and spontaneous persistent currents in mesoscopic aharonov-bohm loops
    (World Scientific Publishing Co., 2005) Kulik, I. O.
    Fixed-number-of-electron mesoscopic or macromolecular conducting ring is shown to support persistent currents due to Aharonov-Bohm flux, and the "spontaneous" persistent currents without the flux when structural transformation in the ring is blocked by strong coupling to the externally azimuthal-symmetric environment. In the free-standing macromolecular ring, symmetry breaking removes the azimuthal periodicity which however is further restored at the increasing field. Three-site ring with one or three electrons represent an interesting quantum system which can serve as a qubit (quantum bit of information) and a qugate (quantum logical gate). © 2005 by World Scientific Publishing Co. Pte. Ltd.