Thermodynamics and structure of hard oblate spherocylinder fluids

Abstract

The equation of state of hard oblate spherocylinders has been calculated for a wide range of densities and reduced core diameters (l* = l/σ, where l and σ are the diameter of the disc core and spherocylinder thickness, respectively) using the Monte Carlo method. The most accurate representation of the data is given by a resummed virial series equation of state based on virial coefficients up to the sixth. Other equations are tested and are found to be less accurate. The fluid structure is discussed in terms of the centres pair correlation function, the surface-surface correlation function, and the coefficients in the spherical harmonic expansion of the pair correlation function. At high densities, neighbouring molecules pack into a short ranged shell structure about a central molecule, in analogy with the hard sphere fluid. We also report Monte Carlo calculations for a fluid of oblate spherocylinders with the addition of a point quadrupole, and examine the effect of the quadrupole-quadrupole forces on both the fluid structure and thermodynamics.