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 wid th ratio. The predictions are based on an Onsager/density functional t heory (DFT), equipped with the exact excluded volume and a somewhat ad hoc resummation of the three and higher particle correlations. For pe rfectly aligned spherocylinders, the (N) nematic to (SmA) smectic A tr ansition is rendered in basic accord with that of previous workers. Wh en rotational disorder is permitted, the calculation becomes sensitive to different implementations of DFT. Although the calculated isotropi c, nematic, smectic A triple point agrees with those of other workers, the location of the N-SmA critical point remains elusive. Present evi dence suggests that the N-SmA transition becomes continuous only in th e limit of highly aligned systems, where there is no orientational ord er to be gained.