Liquid crystal phase diagram of soft repulsive rods and its mapping on the hard repulsive reference fluid

Abstract

The liquid crystal phase diagram of the soft repulsive Kihara fluid has been characterised by means of Monte Carlo simulations, for a selection of elongations of the rod-like particles (L*= 2–7) and over a broad range of temperatures (T *= 1–50). Three qualitatively different regimes of liquid crystalline behaviour are described that are related to the emergence of isotropic–nematic–smectic and isotropic–smectic–solid triple points above specific rod elongations. A mapping of the soft repulsive fluids on hardrepulsive fluids of effective elongation depending on L* and T * is evaluated. Such mapping provides a correct qualitative description of the role of temperature on the liquid crystal phases, and provides a fairly accurate prediction of equations of states and radial functions within the isotropic, nematic and smectic phases. Nevertheless, in comparison to the simulation results, the mapping underestimates the temperature of the isotropic–nematic–smectic triple point, while it overestimates that of the isotropic–smectic–solid one. These results should guide the use of reference hard-body systems to describe the behaviour of soft liquid crystalline materials.

Keywords:

• hard spherocylinder
• soft spherocylinder
• phase diagram
• Tomas Boublick
• liquid crystals
• perturbation theory
• computer simulation

Additional information

Funding

The research activity of our group is currently supported by the Government of Spain [projects CTQ2012-32345 and Consolider-Ingenio CSD2009-00038], and by Junta de Andalucía-FEDER [project P12-FQM-4938].