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

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

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 ?

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

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

MCT fq BMLJ SiO 2

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)

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

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

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 ?

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)

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)

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

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

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

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

Funzioni di correlazione MD simulation

Depletion Interactions Cartoons Depletion Interaction: A Cartoon

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

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

Barsh PRL (phi effect) Temperature

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

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

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

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

MSD logaritmico Slope 1 Slope less than 1

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

Glass glass theory low T high T t

Jumping into the glass aging

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

Bond No-bond t

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

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

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

Equations MCT ! Equazioni base della MCT

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