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One liquid, two glasses. The anomalous dynamics in short ranged attractive colloids Francesco Sciortino Titolo ! Metastability and Landscapes in Complex Systems: Lyon

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In collaboration with ….. Giuseppe Foffi Piero Tartaglia Emanuela Zaccarelli Wolfgang Goetze, Thomas Voigtman, Mattias Sperl Kenneth Dawson collaboratori

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riassunto Outline of the talk The HS glass (and some comparisons with MCT predictions… before getting rid of them) How can we modulate the localization length in the glass ? Study short-range attractive colloids ! -The MCT predictions for SW -Simulations -Experiments Glass-Glass ? Gels ? Hopping Phenomena ?

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van Megen and S.M. Underwood Phys. Rev. Lett. 70, 2766 (1993) HS e MCT (t) HS (slow) dynamics

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Dati Thomas Giuseppe Comparing MD data and MCT predictions for binary HS See next talk by G. Foffi

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MCT fq BMLJ SiO 2

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HS Hard Spheres at =0.58, the system freezes forming disordered aggregates. MCT transition =51.6% 1.W. van Megen and P.N. Pusey Phys. Rev. A 43, 5429 (1991) 2.U. Bengtzelius et al. J. Phys. C 17, 5915 (1984) 3.W. van Megen and S.M. Underwood Phys. Rev. Lett. 70, 2766 (1993) Potential V(r) r (No temperature, only density)

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The mean square displacement (in the glass) The MSD in HS log(t) (0.1 ) 2 MSD

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What if …. Hard Spheres Potential Square-Well short range attractive Potential Can the localization length be controlled in a different way ? What if we add a short-range attraction ? Attractive Glass lowering T

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Log(t) Mean squared displacement repulsive attractive (0.1 ) 2 Figure 1 di Natmat A model with two different localization length How does the system change from one (glass) to the other ?

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The MCT predictions for short-range attractive square well MCT predictions for short range attractive square-well hard-sphere glass (repulsive) Short-range attractive glass fluid Type B A3A3 Fluid-Glass on cooling and heating !! Controlled by Fabbian et al PRE R1347 (1999) Bergenholtz and Fuchs, PRE (1999)

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Non ergodicity parameters for the two glasses Wavevector dependence of the non ergodicity parameter (plateau) along the glass line Fabbian et al PRE R1347 (1999) Bergenholtz and Fuchs, PRE (1999)

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Isodiffusivity Isodiffusivity curves (from MD BHS) Zaccarelli et al PRE 2002

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Correlatori lungo la linea Density-density correlators along the iso-diffusivity locus

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Non-ergodicity factor Non ergodicity parameter along the isodiffusivity curve from MD

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Sub diffusive ! ~(0.1 ) 2 R2 lungo la linea

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Funzioni di correlazione MD simulation

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Depletion Interactions Cartoons Depletion Interaction: A Cartoon

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Science Pham et al Fig 1 Glass samples Fluid samples MCT fluid- glass line Fluid-glass line from experiments Temperature

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Berths PRL (no polymer-with molymer) Colloidal-Polymer Mixture with Re-entrant Glass Transition in a Depletion Interactions T. Eckert and E. Bartsch Phys.Rev. Lett (2002) HS (increasing ) Adding short-range attraction T. Eckert and E. Bartsch

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Barsh PRL (phi effect) Temperature

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Tracing the A4 point Theory and Simulation D PY T MD T PY PY PY + transformation FS et al cond-mat 2003

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q (t)=f q -h q [B (1) ln(t/ ) + B (2) q ln 2 (t/ )]. Phi(t) Same T and, different

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Phi hat q (t q (t)-f q )/h q ^

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X (t)=f X -h X [B (1) ln(t/ ) + B (2) X ln 2 (t/ )]. H(q)

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MSD logaritmico Slope 1 Slope less than 1

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Check List Reentrance (glass-liquid-glass) (both simulation and experiments) A4 dynamics (simulation) Glass-glass transition Check List

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Glass glass theory low T high T t

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Jumping into the glass aging

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Glass glass The attractive glass is not stable ! low T high T Zaccarelli et al cond-mat 2003

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Bond No-bond t

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A summary Nice model for theoretical and numerical simulation Very complex dynamics - benchmark for microscopic theories of super-cooled liquid and glasses (MCT does well!) Model for activated processes Isochoric Diffusivity Maxima - PEL studies (saddles and S conf ) ? A summary

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Volume Fraction Temperature Liquid Repulsive Glass Attractive Glass Gel ? Glass-glass transition Non-adsorbing -polymer concentration glass line Summary 2 (and open questions) ! Activated Processes ? Fig 2 of Natmat

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Structural Arrest Transitions in Colloidal Systems with Short-Range Attractions Taormina, Italy, December A workshop organized by Sow-Hsin Chen (MIT) Francesco Mallamace (U of Messina) Francesco Sciortino (U of Rome La Sapienza) Purpose: To discuss, in depth, the recent progress on both the mode coupling theory predictions and their experimental tests on various aspects of structural arrest transitions in colloidal systems with short-range attractions. Pubblicita Advertisement

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Equations MCT ! Equazioni base della MCT

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The cage effect (in HS) Explanation of the cage and analysis of correlation function Rattling in the cage Cage dynamics log(t) (t) fqfq

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