Hamburg 2001 – scientific programme

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DY: Dynamik und Statistische Physik

DY 43: Kritische Ph
änomene und Phasenumwandlungen

DY 43.3: Talk

Thursday, March 29, 2001, 11:00–11:15, S 7

Poisson-Boltzmann theory and the gas-liquid phase coexistence in colloidal suspensions — •Gernot Klein and Hans Hennig von Grünberg — Fachbereich Physik, Universität Konstanz, 78457 Konstanz

We describe a charge-stabilized colloidal suspension within a Poisson-Boltzmann cell model and calculate the free-energy as well as the compressibility as a function of the colloidal density. The same quantities are then calculated from the linearized Poisson-Boltzmann equation. Comparing non-linear with linear theory, we can test the quality of different linearization schemes. For concentrated suspensions, linearization around the Donnan potential is shown to be preferable to standard Debye-Hückel linearisation. We can furthermore show that the volume-term theory proposed earlier, results if one linearizes around the Donnan potential. Using this linearisation scheme, we find a gas-liquid phase coexistence in linear, but not in non-linear theory. This result seems to indicate that the predicted van-der Waals phase instability in highly deionized colloidal suspensions is an artefact of the linearisation.