Chumalov, A. I.

Crichton, W.

Kargl, F.

Meyer, A.

Monaco, A.

Monaco, G.

Ponkratz, U.

Roitsch, S.

Rüffer, R.

van Bürck, U.

Wortmann, G.

Yue, Yuanzheng

English

    Aalborg UniversitetNuclear Inelastic Scattering in Densified and Hyperquenched GlassesMonaco, A.; Chumalov, A. I.; Yue, Yuanzheng; Crichton, W.; Meyer, A.; van Bürck, U.; Kargl,F.; Rüffer, R.; Monaco, G.; Ponkratz, U.; Roitsch, S.; Wortmann, G.Publication date:2005Document VersionPublisher's PDF, also known as Version of recordLink to publication from Aalborg UniversityCitation for published version (APA):Monaco, A., Chumalov, A. I., Yue, Y., Crichton, W., Meyer, A., van Bürck, U., Kargl, F., Rüffer, R., Monaco, G.,Ponkratz, U., Roitsch, S., & Wortmann, G. (2005). Nuclear Inelastic Scattering in Densified and HyperquenchedGlasses. Abstract from The International Conference on the Application of the Mossbauer Effect, Montpellier,France, .General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            ? Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            ? You may not further distribute the material or use it for any profit-making activity or commercial gain            ? You may freely distribute the URL identifying the publication in the public portal ?Take down policyIf you believe that this document breaches copyright please contact us at vbn@aub.aau.dk providing details, and we will remove access tothe work immediately and investigate your claim.Downloaded from vbn.aau.dk on: November 29, 2020ICAME 2005         Solid state physics, magnetism and lattice dynamics NUCLEAR  INELASTIC  SCATTERING  IN  DENSIFIED  AND  HYPERQUENCHED  GLASSES  A. Monaco1, A. I. Chumakov 1, Y. Z. Yue2, W. Crichton1, A. Meyer3, U. van Bürck3, F. Kargl3,  R. Rüffer1, G. Monaco1, U. Ponkratz1,4, S. Roitsch 4, G. Wortmann4  1European Synchrotron Radiation Facility, F-38043 Grenoble, France 2 Section of Chemistry, Aalborg University , Sohngaardsholmsvej 57 DK-9000 Aalborg, Denmark 3Physik Department E13, Technische Universität Münche , D-85748 Garching, Germany 4 Physik Department 6 Universität Paderborn, D-33098 Paderborn, Germany  In the last years the dynamics of the glassy phase has been extensively investigated: it reveals aspects thatcannot be directly associated neither with the lack of order (relative to the crystalline phase), neither to the loss of mobility (relative to the liquid phase).    With the present study we try to clarify this peculiarity of glasses focusing our interest on the investigation of the so-called Boson Peak (BP) [1].  The BP appears in the vibrational spectra of basically all glasses as an excess of low-frequency modes compared to the Debye model expectations.  The universal character of the BP for glasses leads us to address some basic questions abut its origin:  Is the BP associated with the structural disorder of the system?  Is the non-equilibrium nature of a glass responsible for this phenomenology?  We investigate the connection between vibrational properties, structure and energy landscape description of a glassy system.  To fulfill this task, we probe how the vibrational spectrum of a glass evolves with density and as a function of its thermal history using nuclear inelastic scattering (NIS) [2].    First, we measured the vibrational spectra of densifi d glasses, i.e., systems that remain at elevated density after an external pressure (0-7 GPa) is released.  We obsrved that the density has a pronounced effect on the BP: On increasing the density, the BP moves toward higher energies and decreases in intensity (Fig.1, left), with an evident correlation between position and height of thepeak.  Second, in order to probe how the non-equilibrium nature of a glass can control its dynamics, we measured th vibrational spectra for hyperquenched materials.  In fact, by fast freezing a liquid with various cooling rates, it is possible to obtain glasses with structure and potential energy corresponding to various fictive temperatures Tf (the temperatures where the system falls out of equilibrium during cooling) [3].  Figure 1 (right) shows that the intensity of the BP increases for samples obtained with higher cooling rates (Fig. 1).  This result has been theoretically predicted [4], but till now only partially experimentally verified [5].  The dependence of the BP on density and cooling rate shows that its phenomenology is controlled by both the structure and the energy landscape of the system.    These experimental observations strongly indicate that in glassy systems dynamics, structure and potential energy  are tightly interconnected.  Furthermore, our measurements can help to clarify the validity of theories proposed in the last years to explain the nature of the BP.  [1] see, for instance, A. P. Sokolov et al., Phys. Rev. Lett. 78 (1997) 2405. [2] see, for instance, A. Chumakov et al., Hyperfine interactions 123-124 (1999) 781. [3] C. A. Angell et al., J. Phys.: Cond. Matt. 15 (2003) S1051. [4] T. S. Grigera et al Nature 422 (2003) 289. [5] E. Duval et al., Europhys. Lett. 63 (2003) 778.  0 5 10 15 200,00000,00010,00020,00030,0004 P(GPa) 0 1 2 7  Energy [meV]g(E)/E2  [meV-3]  0 5 10 15 20024 rapidly cooled slowly cooled very slowly cooled Energy [meV]Intensity [a. u.]   Figure 1. Left: Reduced density of states RVDOS g(E)/E2 of Na2FeSi3O8 for different densities obtained pressurizing the sample at 0, 1, 2, and 7 GPa.  Right: Energy spectra of NIS for Na2O/FeO/CaO/SiO2 glasses prepared with various quenching rates.   

Nuclear Inelastic Scattering in Densified and Hyperquenched Glasses

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Nuclear Inelastic Scattering in Densified and Hyperquenched Glasses

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