Browsing by Author "Argyriou, DN"

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    Inelastic neutron scattering from cubic stabilised zirconia
    (Australian and New Zealand Institutes of Physics, 1994-02-09) Argyriou, DN; Elcombe, MM
    Phonon dispersion curves have been measured for three cubic stabilised zirconias (CSZ) with varying amounts of oxygen vacancies (Zr(Y)O1.193, Zr(Ca)O1.875, Zr(Y)O1.805), using a triple axis spectrometer. We have been able to observe transverse (TA) and longitudinal acoustic (LA) branches for these crystals. However in agreement with previous work, and despite an exhaustive search in (Q,ω) space, optic modes were not observed 1. The behaviour of the LA and TA branches is atypical, in that phonons become increasingly broader, and weaker close to the Brillouin zone boundary. This is particularly the case for the [ζζ0] direction, where the TA2 branch disappears beyond ζ=0.45. This atypical behaviour has been speculated to be caused by to the defect fluorite structure of CSZ. Recently a reliable model of the static structure has been determined 2 and has been used here to explain the observed inelastic neutron scattering observations. To understand the effect of the defect structure of CSZ to the observed neutron measurements, lattice dynamical calculations have been carried out on the basis of the static structure. These calculations show that the stability of CSZ is particular sensitive to the [100] interactions between oxygen atoms. They show that either relatively small variations in the force constants for this interaction, associated with variations of the 0-0 bondlengths in the defect structure, or the incorporation of vacancies into the structure can render the [(ζζ0] TA2 mode mutable. This is in agreement with the experimental results which shows that this mode disappears rapidly. These calculations also show a general broadening of all phonon branches. This makes the measurer lent of the optic phonon particularly difficult. It is found therefore that the static defect model of CSZ is consistent with the inelastic neutron scattering measurements.
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    The instrument suite of the European Spallation Source
    (Elsevier B. V., 2020-01-10) Andersen, KH; Argyriou, DN; Jackson, AJ; Houston, J; Henry, PF; Deen, PP; Toft-Petersen, R; Beran, P; Strobl, M; Arnold, T; Wacklin-Knecht, H; Vivanco, R; Parker, SF; Gussen, A; Kanaki, K; Scionti, G; Olsen, MA; Arai, M; Schmakat, Ph; Lechner, RE; Niedermayer, Ch; Schneider, H; Zanetti, M; Petrillo, C; Moreira, FY; Stepanyan, S; Luna, P; Calzada, E; Stahn, J; Voigt, J; Dupont, T; Hanslik, R; Siemers, DJ; Udby, L; Chowdhury, MAH; Klauser, Ch; Rouijaa, M; Lehmann, E; Heynen, A; Bustinduy, I; Schwaab, A; Raspino, D; Scatigno, C; del Moral, OG; Kiehn, R; Aprigliano, G; Zanatta, M; Huerta, M; Bellissima, S; Lerche, M; Holm-Dahlin, S; Huerta, M; Christensen, NB; Lohstroh, W; Gorini, G; Fenske, J; Hansen, UB; Klauser, C; Rodrigues, S; Müller, M; Gorini, G; Bovo, C; Hall-Wilton, R; Fabrèges, X; Siemers, DJ; Khaplanov, A; Tsapatsaris, N; Taylor, J; Christensen, M; Schefer, J; Woracek, R; Tozzi, P; Müller, M; Carlsen, H; Olsen, MA; Orecchini, A; Di Fresco, L; Paciaroni, A; Bovo, C; Magán, M; Hauback, BC; Elmer, J; Heenan, RK; Piscitelli, F; Masi, F; Bakedano, G; Klimko, S; De Bonis, A; Fedrigo, A; Lukáš, P; Frielinghaus, H; Stahn, J; Schweika, W; Markó, M; Pfeiffer, D; Kirstein, O; Di Fresco, L; Schreyer, A; Orszulik, A; Nowak, G; Butterweck, S; Šaroun, J; Paciaroni, A; Kolevatov, R; Lehmann, EH; Filges, U; Schreyer, A; Koenen, M; Bustinduy, I; Magán, M; Feygenson, M; Cooper, JFK; Abad, E; Senesi, R; Longeville, S; Llamas-Jansa, I; Schulz, M; Birk, JO; Sharp, M; Galsworthy, P; Šaroun, J; Martínez, J; Hiess, A; Holm-Dahlin, S; Filges, U; Pullen, SA; Guyon Le Bouffy, J; Schefer, J; Lukáš, P; Udby, L; Kozielewski, T; Niedermayer, C; Sacchetti, F; Hartl, M; Jaksch, S; Salhi, Z; Brückel, T; Aguilar, J; Aguilar, J; Seifert, M; Bordallo, HN; Robillard, T; Villacorta, FJ; Herranz, I; del Rosso, L; Hauback, BC; Orecchini, A; Fabrèges, G; Fenske, J; Neuhaus, J; Schillinger, B; Abad, E; Kittelmann, T; Lefmann, K; Seifert, M; Neuhaus, J; Herranz, I; Kolevatov, R; Annighöfer, B; Oksanen, E; Morgano, M; Laszlo, G; Freeman, PG; Kennedy, SJ; Bertelsen, M; Bellissima, S; Alba-Simionesco, C; Markó, M; Mezei, F; Chowdhury, M; Halcrow, W; Jestin, J; Lieutenant, K; Babcock, E; Rønnow, HM; Engels, R; del Moral, OG; Vickery, A; Rouijaa, M; Lavie, P; Petersson Årsköld, S; Glavic, A; Désert, S; Mannix, D; Scatigno, C; Petry, W; Christensen, NB; Violini, N; Villacorta, FJ; Porcher, F; Glavic, A; Scionti, G; Zanetti, M; Fernandez-Alonso, F; Rønnow, HM; Mosconi, M; Olsson, M; Stepanyan, S; Petrillo, C; del Rosso, L; Harbott, P; Sacchetti, F; Bertelsen, M; Kämmerling, H; Andreani, C; Schulz, M; Colognesi, D; Luna, P; Loaiza, L; Turner, D; Martínez, JL; Tartaglione, A; Sordo, F; Llamas-Jansa, I; Schmakat, P; Lechner, RE; Poqué, A; Fernandez-Alonso, F; Colognesi, D; Tartaglione, A; Morgano, M; Webb, N; Loaiza, L; Whitelegg, L; Petry, W; Iversen, K; Vivanco, R; Tozzi, P; Goukassov, A; Schillinger, B; Carlsen, H; Masi, F; Christensen, M; Nowak, G; Nightingale, J; Schütz, S; Lopez, CI; Langridge, S; Schütz, S; Nagy, G; Zanatta, M; Andreani, C; Lefmann, K; Lohstroh, W; Mosconi, M; Senesi, R; Stefanescu, I; Bakedano, G; Hagen, ME; Wischnewski, A; Bourges, P; Hansen, UB; De Bonis, A; Kiehn, R; Parker, SF; Iversen, K; Sordo, F; Freeman, PG; Birk, JO; Rodríguez, DM; Ansell, S
    An overview is provided of the 15 neutron beam instruments making up the initial instrument suite of the European Spallation Source (ESS), and being made available to the neutron user community. The ESS neutron source consists of a high-power accelerator and target station, providing a unique long-pulse time structure of slow neutrons. The design considerations behind the time structure, moderator geometry and instrument layout are presented. The 15-instrument suite consists of two small-angle instruments, two reflectometers, an imaging beamline, two single-crystal diffractometers; one for macromolecular crystallography and one for magnetism, two powder diffractometers, and an engineering diffractometer, as well as an array of five inelastic instruments comprising two chopper spectrometers, an inverse-geometry single-crystal excitations spectrometer, an instrument for vibrational spectroscopy and a high-resolution backscattering spectrometer. The conceptual design, performance and scientific drivers of each of these instruments are described. All of the instruments are designed to provide breakthrough new scientific capability, not currently available at existing facilities, building on the inherent strengths of the ESS long-pulse neutron source of high flux, flexible resolution and large bandwidth. Each of them is predicted to provide world-leading performance at an accelerator power of 2 MW. This technical capability translates into a very broad range of scientific capabilities. The composition of the instrument suite has been chosen to maximise the breadth and depth of the scientific impact of the early years of the ESS, and provide a solid base for completion and further expansion of the facility. © 2020 The Authors. Published by Elsevier B.V. Open access article under the CC BY-NC-ND license.
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    Interlayer tuning of electronic and magnetic properties in honeycomb ordered Ag3LiRu2O6
    (Royal Society of Chemistry, 2010-10-07) Kimber, SAJ; Ling, CD; Jonathan, D; Morris, P; Chemseddine, A; Henry, PF; Argyriou, DN
    We report a switching of electronic, magnetic and lattice properties in honeycomb ruthenates by interlayer cation exchange. The new material Ag3LiRu2O6 was made by ion-exchange of the ordered Li/Ru honeycomb material Li2RuO3 in an AgNO3 melt at 200°C. Neutron powder diffraction and electron microscopy show that the Li/Ru order is preserved in the honeycomb layers, however, significant stacking disorder is found between layers. In contrast to Li2RuO3, which is insulating, dimerised and diamagnetic, Ag3LiRu2O6 has low electrical resistivity (0.01 ohm cm−1) and a large magnetic susceptibility at room temperature. This is attributed to the electronic influence of the highly polarisable interlayer Ag+ cation. The combination of two dimensionality, good conductivity and stacking disorder means this family of materials have potential for thermoelectric applications. © 2010, Royal Society of Chemistry
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    Raman and neutron scattering study of partially deuterated l-alanine: evidence of a solid-solid phase transition
    (Wiley-VCH Verlag Berlin, 2009-12-21) de Souza, JM; Freire, PTC; Argyriou, DN; Stride, JA; Barthes, M; Kalceff, W; Bordallo, HN
    Raman and neutron experiments using specific isotope labeling were combined in order to study the dynamics and structure Of L-alanine. Inelastic neutron and Raman scattering data of C2H4(ND2)CO2D are discussed in relation to the doubling of the lattice parameter a observed by means of neutron powder diffraction in C2D4 (NH2)CO2H. The major changes accompanying the phase transition are found in the vibrational frequencies involving the torsional vibration tau(CO2-) which is clearly affected by the hydrogen bonds between the protons of the ammonium group and the oxygen atoms of the carboxylate group. At lower temperatures the rearrangement of identifiable hydrogen bonds induces changes in the bending vibration delta(ND3), confirming some orientational disorder. © 2009, Wiley-VCH Verlag Berlin