A perturbed-chain equation of state based on Wertheim TPT for the fully flexible LJ chains in the fluid and solid phases.

Abstract

In the framework of thermodynamic perturbation theory (TPT), a new perturbed-chain equation of state (EOS) is presented for a fully flexible Lennard-Jones (LJ) chain system. The EOS is the sum of repulsive and perturbation contributions. The reference term of the EOS is derived based on first- and second-order TPT of Wertheim for the chains interacting with each other through the Weeks-Chandler-Anderson potential model. In order to derive the perturbation term, we have used the radial distribution function of the hard-chain system with a chain range of m = 2-10 and packing fraction range of η = 0.10-0.72, which cover the entire density range from vapor to solid phases. The performance of the EOS is tested against simulation data of the compressibility factor, residual internal energy, and phase equilibrium. A close agreement was observed across all cases. The EOS has three pure component parameters and is able to describe the global vapor-liquid-solid phase diagram of the LJ chain.