one liquid, two glasses. the anomalous dynamics in short ranged attractive colloids francesco...

One liquid, two glasses. The anomalous dynamics in short

ranged attractive colloids

Francesco Sciortino

Email: francesco.sciortino@phys.uniroma1.it

MIT, November 21, 2003

Outline of the talk

The HS glass (and some comparisons with MCT predictions)

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)

(t) HS (slow) dynamics

Comparing MD data and MCT predictions for binary HS

G. Foffi et al, PRE, in press

BMLJ SiO2

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)

log(t)

(0.1 )2

MSD

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 ?

lowering T

Log(t)

Mean squared displacement

repulsiveattractive

(0.1 )2

A model with two different localization length

How does the system change from one (glass) to the other ?

MCT predictions for short range attractive square-well

hard-sphere glass

(repulsive)

Short-range attractive glass

fluid

Type B

A3

Fluid-Glass on cooling and heating !!

Controlled by

Fabbian et al PRE R1347 (1999)Bergenholtz and Fuchs, PRE 59 5708 (1999)

Wavevector dependence of the non ergodicity parameter

(plateau) along the glass line

Fabbian et al PRE R1347 (1999)Bergenholtz and Fuchs, PRE 59 5708 (1999)

Isodiffusivity curves (from MD BHS)

Zaccarelli et al PRE 2002

Density-density correlators along the iso-diffusivity locus

Non ergodicity parameter along the isodiffusivity curve from MD

Sub diffusive !

~(0.1 )2

MD simulation

Depletion Interaction:A Cartoon

Glass samplesFluid samples

MCT fluid-glass

line

Fluid-glass line from

experiments

Tem

pera

ture

Colloidal-Polymer Mixture with Re-entrant Glass Transition in a Depletion Interactions

T. Eckert and E. Bartsch

Phys.Rev. Lett. 89 125701 (2002)

HS (increasing )

Addingshort-rangeattraction

T. Eckert and E. Bartsch

Temperature

Tracing the A4 point

Theory and Simulation

D 1.897PY-0.3922

TMD 0.5882TPY - 0.225

PY PY +transformation

FS et al PRL in press

q(t)=fq-hq [B(1) ln(t/) + B(2)q ln2(t/)].

Same T and, different

q(tq(t)-fq)/hq^

X(t)=fX-hX [B(1) ln(t/) + B(2)X ln2(t/)].

Slope 1

Slope less than 1

Reentrance (glass-liquid-glass) (both simulation and experiments)

A4 dynamics √ (simulation)

Glass-glass transition

Check List

√

low T

high T

t

Jumping into the glass

The attractive glass is not stable !low T

high T

Zaccarelli et al PRL 2003

t

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 Sconf) ?

A summary

Volume Fraction

Tem

pera

ture

Liquid

RepulsiveGlass

Attractive Glass

Gel

?Glass-glass transition

Non

-ads

orbi

ng -

poly

mer

con

cent

rati

on glass line

Summary 2 (and open questions) !

Activated Processes ?

Structural Arrest Transitions in Colloidal Systems  with Short-Range Attractions

 Messina, Italy, December 17 2003.

 A workshop organized by

Sow-Hsin Chen (MIT) (sowhsin@mit.edu)Francesco Mallamace (U of Messina) (mallamac@mail.unime.it)

Francesco Sciortino (U of Rome La Sapienza) (francesco.sciortino@phys.uniroma1.it) 

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.

http://server1.phys.uniroma1.it/DOCS/TAO/

Advertisement

Equations MCT !

The cage effect

(in HS)

Rattling in the cage

Cage dynamics

log(t)

(t)

fq