Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 20: Focus: Magnetic Soft Matter II

CPP 20.5: Talk

Wednesday, March 25, 2009, 10:45–11:00, ZEU 222

Gas–liquid critical behavior in fluids of soft-repulsive charged dumbbells — •Heiko Braun and Reinhard Hentschke — Fachbereich Mathematik und Naturwissenschaften, Bergische Universität Wuppertal, D-42097 Wuppertal, Germany

The existence of gas-liquid coexistence in dipolar fluids with no other contribution to attractive interaction than dipole-dipole interaction is a basic and open question in the theory of fluids. Recent MC work by Camp and coworkers [1] indicates that a fluid of charged hard dumbbells does exhibit g-l coexistence. This system has the potential to answer the above fundamental question, because the charge-to-charge separation d on the dumbbells may be reduced to, at least in principle, yield the dipolar fluid limit. Here we present MD results for the g-l phase behavior including the critical point of charged soft dumbbells for fixed dipole moment and fixed charges as function of d. We do find a g-l critical point at finite temperature for fixed dipole moment at small d. In this limit, however, we also find that the dumbbells form reversible networks so that the transition possibly is due to the mechanism suggested by Tlusty and Safran [2] for reversible networks.
[1] G. Ganzenmüller, P. J. Camp, J. Chem. Phys. 126, 191104 (2007)

[2] T. Tlusty, S. A. Safran, Science 290, 1328 (2000)