ISOTROPIC, NEMATIC AND SMECTIC-A PHASES IN FLUIDS OF HARD SPHEROCYLINDERS

A phase diagram with accompanying order parameters has been calculated for the fluid phases of hard spherocylinders with perfect and partial orientational order as a function of the spherocylinder length to width ratio. The predictions are based on an Onsager/density functional theory (DFT), equipped with the exact excluded volume and a somewhat ad hoc resummation of the three and higher particle correlations. For perfectly aligned spherocylinders, the (N) nematic to (SmA) smectic A transition is rendered in basic accord with that of previous workers. When rotational disorder is permitted, the calculation becomes sensitive to different implementations of DFT. Although the calculated isotropic, nematic, smectic A triple point agrees with those of other workers, the location of the N-SmA critical point remains elusive. Present evidence suggests that the N-SmA transition becomes continuous only in the limit of highly aligned systems, where there is no orientational order to be gained.