Regensburg 2007 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
CPP: Fachverband Chemische Physik und Polymerphysik
CPP 4: Colloids and Nanoparticles II: Effective Interactions
CPP 4.4: Vortrag
Montag, 26. März 2007, 15:00–15:15, H37
Structure of charged colloids in three dimensions and in films: How important is the salt ? — •Sabine Klapp1,2, Dan Qu1, and Regine von Klitzing1 — 1Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin — 2Institut für Theoretische Physik, Technische Universität Berlin
Using computer simulations and (hypernetted chain) integral equations we investigate the structure of charged colloidal suspensions in bulk and in spatial confinement (film geometry), focusing on the identification of characteristic length scales. The calculations are based on 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 κ 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 ξ∝ φ−1/3 for the average particle distance ξ=2π/qmax in three spatial dimensions describes the results only for low ionic strength, that is for relatively long–ranged potentials characterized by small values of κ. On the other hand, systems with larger ionic strengths 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 for suspensions with low salt concentration are in excellent quantitative agreement with experimental results for charged Silica particles.
S. H. L. Klapp, D. Qu, and R. v. Klitzing, J. Phys. Chem. B, in press.