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Small molecules that form liquid crystals typically consist of a rigid core with flexible tails on one end or on both ends. To date, most computer simulation studies have used completely rigid models such as hard spherocylinders: cylinders, characterized by their length/diameter ratio L D , with hemispherical end caps. We have studied a model consisting of spherocylinders with L D = 4, with a flexible tail attached to each end. The tails are 'ideal' in the sense that they have no volume. Using Monte Carlo simulations the phase behaviour of this model was studied and, for comparison, the behaviour of hard spherocylinders with L D = 4 without tails was studied as well. The addition of the tails is found to stabilize the smectic-A phase at a lower pressure, and the nematic phase disappears. In the smectic-A and crystal phases, the smectic layers are further apart when tails are added. The structure of the layers and the smectic-A-crystal transition pressure change only a little. For both models close to melting the crystal consists of ordered layers, but there is almost no correlation between particle positions in neighbouring layers. In fact, the layer coupling is so weak that in a long simulation the layers are found to glide over each other. As the pressure is increased the crystal gradually becomes more ordered and the crystalline layers ultimately 'lock' into place. [ABSTRACT FROM AUTHOR]

Computer simulations are used to investigate the recent prediction (R. van Roij et al., 1995, Phys. Rev., E52, R1277) of transverse interlayer order in the smectic-A phase of hard spherocylinders. For short rods, and close to the melting point of the smectic-A phase, a fraction of about one per cent of the particles are in the transverse interlayer state. For longer rods and further away from the melting transition a much lower fraction is found. Possible implications for interlayer diffusion and end-over-end rotational diffusion are discussed. [ABSTRACT FROM AUTHOR]