New SAFT-VR equation of state based on Morse potential

Abstract

Abstract In this work, a new statistical associating fluid theory with variable range (SAFT-VR) equation of state (EOS) for the Morse fluids has been developed. Monte Carlo (MC) simulations have been performed to determine the first and second order perturbative contributions of Barker and Henderson (BH) perturbation theory over wide range of density, temperature and potential ranges. In addition to perturbative terms, pressure and internal energy of Morse fluid have been simulated and compared with theoretical results. In development of new EOS, an exact analytic solution of the Percus-Yevick (PY) integral equation for hard sphere radial distribution function (RDF) has been implemented into calculation of the first and second terms of BH theory. Our results showed that there are good agreement between MC simulation data and analytical solution of hard sphere RDF. In the case of BH first order term, excellent agreement was obtained. It is found that, the new EOS is able to predict the perturbative Helmholtz free energy, pressure and residual internal energy of Morse fluids over wide range of thermodynamic conditions. Finally, the new EOS has been utilized to correlate vapor pressure and saturated liquid density of pure components. Obtained results in this work prove that considering Morse as potential function can lead us to achieve an accurate SAFT-based EOS.