A Molecular-Based Equation of State for Mixtures of Cylindrically Symmetric Hard Bodies

A molecular-based equation of state (EOS) for cylindrically symmetric hard bodies (CSHB) is extended to mixtures of anisomorphic particles. Monte Carlo simulations are conducted in the isobaric–isothermal ensemble to validate combining and mixing rules, particularly the Isihara–Hadwiger theorem, and in the canonical ensemble to assess a modification of the force field by determining the coefficients associated with a second-order Barker–Henderson thermodynamic perturbation theory (BH-TPT). The Parsons–Lee approximation performs better for elongated particles, whereas scaled particle theory is more accurate for discotic cylinders. The proposed rules satisfactorily describe multicomponent systems. The convex square-well formulation reproduces the first-order BH-TPT coefficient, while modifying the second-order coefficient improves agreement within the range of molecular parameters relevant to phase equilibria. The CSHB EOSs generally outperform SAFT-VR-SSW for the binary and ternary vapor–liquid equilibria investigated, including the azeotrope of C2H4 + CO2.