The high density equation of state and solid-fluid equilibrium in systems of freely jointed chains of tangent hard spheres

Abstract

We present a study of the solid-fluid phase equilibrium for systems of freely jointed chains of tangent hard spheres using Monte Carlo computer simulation. Extensive calculations of the fluid and solid phase equations of state have been made. Our results for the fluid properties are compared with various theoretical equations of state which have been proposed for these systems. A method for calculating the solid phase free energy of chain molecules has been developed based on finding a reversible path to an Einstein crystal. The stable solid phase structure of these systems approximates cubic close packing of the atoms without long range orientational ordering of the bond vectors. The contribution to the solid phase free energy from the configurational degeneracy has been approximated by the expression developed by Huggins. The dependence of the solid phase thermodynamics upon the chain conformation has been studied and solid-fluid phase diagrams for chains with lengths ranging from three through eight atoms have been determined.