NEMATIC TO SMECTIC-A TRANSITION OF PARALLEL DIPOLAR HARD SPHEROCYLINDERS AND ELLIPSOIDS, A HYPERNETTED CHAIN EQUATION STUDY

The thermodynamic, dielectric, and structural properties of systems of dipolar hard spherocylinders and ellipsoids with perfect nematic order are investigated by means of the hypernetted chain (HNC) equation. The density, temperature domain for which the HNC equation admits a stable solution is determined. For spherocylinders a large increase of the main peak of the total structure factor in the vicinity of the stability limit of the HNC equation is, tentatively, associated with the onset of a nematic-smectic-A transition. The situation seems less clear for dipolar ellipsoids, though the results are in many aspects qualitatively similar to the spherocylinder case. The pair structure near the transition is analyzed. It is not characteristic of any of the smectic-A phase structures typical of strongly polar liquid crystals. This is probably a consequence of the highly symmetric nature of the model. © 1990 American Institute of Physics.