Browsing by Author "Russina, M"

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    Diffuse scattering and QENS study of copper chalcogenides
    (Australian Institute of Physics, 2009-02-05) Danilkin, SA; Avdeev, M; Studer, AJ; Ling, CD; Macquart, RB; Russina, M; Izaola, Z
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    Dynamical transition in a large globular protein: macroscopic properties and glass transition
    (Elsevier, 2010-01) Kealley, CS; Sokolova, AV; Kearley, GJ; Kemner, E; Russina, M; Faraone, A; Hamilton, WA; Gilbert, EP
    Hydrated soy-proteins display different macroscopic properties below and above approximately 25% moisture. This is relevant to the food industry in terms of processing and handling. Quasi-elastic neutron spectroscopy of a large globular soy-protein, glycinin, reveals that a similar moisture-content dependence exists for the microscopic dynamics as well. We find evidence of a transition analogous to those found in smaller proteins, when investigated as a function of temperature, at the so-called dynamical transition. In contrast, the glass transition seems to be unrelated. Small proteins are good model systems for the much larger proteins because the relaxation characteristics are rather similar despite the change in scale. For dry samples, which do not show the dynamical transition, the dynamics of the methyl group is probably the most important contribution to the QENS spectra, however a simple rotational model is not able to explain the data. Our results indicate that the dynamics that occurs above the transition temperature is unrelated to that at lower temperatures and that the transition is not simply related to the relaxation rate falling within the spectral window of the spectrometer. © 2010, Elsevier Ltd.
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    Neutron scattering study of short-range correlations and ionic diffusion in copper selenide
    (Springer, 2011-02-01) Danilkin, SA; Avdeev, M; Sakuma, T; Macquart, RB; Ling, CD; Russina, M; Izaola, Z
    The paper reports the results of a neutron scattering study of Cu(2-delta)Se superionic compounds. The crystallographic model fitted to the diffraction data shows the occupation of 8c and 32f sites by Cu atoms. Observed diffuse background is related to correlated thermal vibrations of Se and Cu atoms, with Sea dagger"Cu (8c,32f) and Cu (8c)a dagger"Cu (8c) correlations being most important. The quasi-elastic neutron experiments show the decrease of the self-diffusion coefficient with the deviation from the stoichiometry due to the longer residence time of Cu ions between diffusion hops. Combination of neutron diffraction, diffuse scattering and quasi-elastic scattering experimental data suggests that the Cu atoms diffuse between the nearest 8c sites through the 32f sites. © 2011, Springer.
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    Quasi-elastic neutron scattering study of diffusion in Cu-Se superionic conductor
    (Malaysian Nuclear Agency, 2009-06-29) Danilkin, SA; Avdeev, M; Ling, CD; Macquart, RB; Russina, M; Izaola, Z
    Copper selenide is a mixed ionic-electronic conductor and received attention from the technological and physical point of view in particular due to a high ionic conductivity. According to [1, 2] only a fraction of Cu atoms takes part in the ionic transport in Cu{sub 2-x}Se compounds: the number of mobile atoms is about 1/3 - 1/8 of the total cation concentration in stoichiometric Cu{sub 2}Se and decreases with x causing the ionic conductivity to drop. This conclusion was based on the assumption that Cu mobility does not depend on composition. Therefore the QENS study is of interest because the width and intensity of quasi-elastic peak associated with Cu diffusion are directly related to Cu coefficient of self-diffusion and the number of mobile ions, respectively. This paper presents results of QENS measurements performed on Cu{sub 1.77}Se, Cu{sub 1.90}Se and Cu{sub 1.98}Se compounds at 313 and 430 K. We found that in Cu{sub 1.98}Se the quasielastic component is not observed in ordered non-superionic {alpha}-phase at T = 313 K, however it is clearly seen in superionic {beta}-phase at T=430 K. By contrast the Cu{sub 1.77}Se compound which is superionic at ambient temperature has relatively small quasielastic component showing little difference between 313 and 430 K. The analysis shows that fraction of Cu atoms which takes part in the ionic transport indeed decreases with x in general agreement with papers [1, 2], but not vanishes at x = 0.23. [1] R.A. Yakshibaev et al., Sov. Phys. Solid State, 26 2189 (1984) [2] M.A. Korzhuev, Phys. Solid State 40 217 (1998)