Avoidance model for soft particles. II. Positional ordering of charged rods

The phase diagram of parallel, charged spherocylinders is computed. The top ology of the diagram is found to be similar to the uncharged one, but then are several qualitative changes. Regions of phase coexistence are significa ntly narrower and positional ordering is stabilized by the electrostatic re pulsions. The nematic phase occupies a very narrow zone. We suggest that so ft repulsions between surfactant micelles may be responsible for the absenc e of a nematic phase in most surfactant systems. We also present comparison s with the observed nematic-smectic phase transition for fd and tobacco mos aic virus particles.