Teil eines Buches,
Competing length scales in threedimensional and confined charged colloids
Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, Genova, Italy, (9-13 July 2007)
Zusammenfassung
We investigate the structure formation of charged colloidal suspensions
in bulk and in spatial confinement (film geometry), focussing on the identification
of characteristic length scales.
The calculations are
based on computer simulations and (hypernetted chain) integral equationson, using
an effective description of the multicomponent colloidal suspension
via a screened Coulomb (DLVO) potential between the macroions. The range
of the interaction is controlled by the inverse Debye length $\kappa$
determined by the concentrations
of counterions and the ionic strength of additional salt (if present).
Concerning bulk properties, we find that the commonly accepted
power law $\xi\phi^-1/3$
for the average particle distance $\xi=2\pi/q_max$
in three spatial dimensions
describes the results only for low ionic
strength, that is for relatively long--ranged potentials characterized
by small values of $\kappa$. On the other hand, systems with larger ionic strengths
and, consequently, more short--ranged interactions do
not obey such power--law behavior and rather resemble an uncharged hard--sphere
fluid, where the relevant length scale is the particle diameter. Similar observations
hold in a film geometry. For both geometries, our results
are in excellent quantitative agreement with experimental results for charged Silica particles S.K.L. Klapp, D. Qu, R.v. Klitzing, J. Phys. Chem. B 111, 1296 (2007).
