one liquid, two glasses. the anomalous dynamics in short ranged attractive colloids francesco...
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One liquid, two glasses. The anomalous dynamics in short
ranged attractive colloids
Francesco Sciortino
Email: [email protected]
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) ([email protected])Francesco Mallamace (U of Messina) ([email protected])
Francesco Sciortino (U of Rome La Sapienza) ([email protected])
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/
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Equations MCT !
The cage effect
(in HS)
Rattling in the cage
Cage dynamics
log(t)
(t)
fq