THE HARD ELLIPSE LIQUID - AN INTEGRAL-EQUATION STUDY

We investigate the structural and thermodynamic properties of the isotropic phase of the hard ellipse liquid for several length-to-breadth ratios (2,4,6), using the hypernetted chain (HNC) and Percus-Yevick (PY) integral equation theories. A comparison with the recent simulations of Cuesta and Frenkel [Phys. Rev. A 42, 2126 (1990)] is made. Satisfactory agreement is found with PY theory for small aspect ratios, while for larger ones, HNC results become superior. In addition, HNC (but not PY) predicts the orientational instability of the isotropic phase at a finite density for systems of aspect ratios 4 and 6, in good agreement with computer simulation results. In order to investigate the order of the orientational phase transition, density functional theories (DFT) calculations are carried out using as input the direct correlation functions of the isotropic liquid obtained in this work. No first-order transition is found within the version of DFT used herein.