Statistical Theory of Liquid Crystalline Orderings in Hard Rod Fluids

A review is given of theoretical studies on systems of rod-like molecule with simple shape ( cylinders, spherocylinders, square rods,...). The role of hard-core repulsion in liquid crystalline orderings are mainly discussed. It is shown that the excluded volume effect due to the hard-core repulsion stabilizes not only the orientational order but also positional ordering of the smectic A density wave in cylindrical molecules.