An equation of state for hard dumbell fluids

Abstract

Abstract Monte Carlo simulations are reported for 45 state points of the hard dumbell system covering elongations l/σ from 0·2 to 1·0 and densities σd 3 from 0·2 to 0·9 (l is the bond length, σ the atom diameter and the d the diameter of a sphere with the same volume as the dumbell). The calculated compressibility factors, P/ρkT, together with the second virial coefficients reported by Isihara, have been used in a least squares evaluation of the constants in an equation of state that expresses the compressibility factor as a function of elongation and density. The fitted equation reproduces the virial coefficients to within about 0·2 per cent and the compressibility factors to within about 0·4 per cent. For the limiting case of hard spheres (l = 0) it reduces to the Carnahan-Starling equation. Expressions have been derived for calculating the isothermal compressibility, residual free energy and residual chemical potential from the equation.