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The Landau free energy of hard ellipses obtained from microscopic simulations
Alan M Luo1, Leonard M C Sagis1, Patrick Ilg1
1ETH Zürich, Department of Materials, Polymer Physics, CH-8093 Zürich, Switzerland.
Abstract:
Systems of two-dimensional hard ellipses of varying aspect ratios and packing fractions are studied by Monte Carlo simulations in the generalised canonical ensemble. From this microscopic model, we extract a coarse-grained macroscopic Landau-de Gennes free energy as a function of packing fraction and orientational order parameter. We separate the free energy into the ideal orientational entropy of non-interacting two-dimensional spins and an excess free energy associated with excluded volume interactions. We further explore the isotropic-nematic phase transition using our empirical expression for the free energy and find that the nature of the phase transition is continuous for the aspect ratios we studied.
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