TY - JOUR

T1 - The isotropic-nematic phase transition in uniaxial hard ellipsoid fluids

T2 - Coexistence data and the approach to the Onsager limit

AU - Camp, Philip J.

AU - Mason, Carl P.

AU - Allen, Michael P.

AU - Khare, Anjali A.

AU - Kofke, David A.

PY - 1996/8/15

Y1 - 1996/8/15

N2 - The isotropic-nematic (I-N) phase transition in hard ellipsoid fluids has been studied by computer simulation, using the Gibbs-Duhem integration technique introduced by Kofke; and theoretically, using Onsager theory and the Parsons-Lee improvement. In the simulations, the I-N coexistence line is mapped out in the P-x plane, where P is the pressure and x is the elongation, by numerically integrating a Clapeyron-like first-order differential equation, using constant-pressure simulation data for the two coexisting phases. The elongation range 5≤x≤20 has been studied, using independent starting points provided by chemical potential calculations and thermodynamic integration of the equation of state at x = 5,20, plus a direct Gibbs ensemble simulation at x = 20. The Onsager-Parsons-Lee theory has been applied to the I-N phase transition for aspect ratios up to x = 1000, affording an accurate investigation of the approach to the Onsager limit for this model. This involved the numerical computation of the orientation-dependent second virial coefficient in a way that avoids expansions in Legendre polynomials, so as to be accurate at high elongation. Over the elongation range studied here, agreement between simulation and the Parsons-Lee theory is good.

AB - The isotropic-nematic (I-N) phase transition in hard ellipsoid fluids has been studied by computer simulation, using the Gibbs-Duhem integration technique introduced by Kofke; and theoretically, using Onsager theory and the Parsons-Lee improvement. In the simulations, the I-N coexistence line is mapped out in the P-x plane, where P is the pressure and x is the elongation, by numerically integrating a Clapeyron-like first-order differential equation, using constant-pressure simulation data for the two coexisting phases. The elongation range 5≤x≤20 has been studied, using independent starting points provided by chemical potential calculations and thermodynamic integration of the equation of state at x = 5,20, plus a direct Gibbs ensemble simulation at x = 20. The Onsager-Parsons-Lee theory has been applied to the I-N phase transition for aspect ratios up to x = 1000, affording an accurate investigation of the approach to the Onsager limit for this model. This involved the numerical computation of the orientation-dependent second virial coefficient in a way that avoids expansions in Legendre polynomials, so as to be accurate at high elongation. Over the elongation range studied here, agreement between simulation and the Parsons-Lee theory is good.

UR - http://www.scopus.com/inward/record.url?scp=0001443834&partnerID=8YFLogxK

U2 - 10.1063/1.472146

DO - 10.1063/1.472146

M3 - Article

AN - SCOPUS:0001443834

VL - 105

SP - 2837

EP - 2849

JO - The Journal of Chemical Physics

JF - The Journal of Chemical Physics

SN - 0021-9606

IS - 7

ER -