Density and isothermal compressibility of ionic liquids from perturbed hard-dimer-chain equation of state

A perturbed hard-sphere chain equation of state (PHSC EOS) has been previously employed for modelling the density and isothermal compressibility of some ionic liquids (ILs). This EOS considered chains that interact through a range-parameter of Yukawa potential with l.8. In this work, we have assessed the role of hard-dimers to present an alternative perturbed hard-chain (PHC) EOS for ILs. The performance of the perturbed hard-dimer chain (PHDC) model has been checked for density over a wide range of temperatures and pressures from 273–472 K and 0.1–249.3 MPa, respectively. Our calculations on the density of studied systems reproduce very accurately the literature data, the overall average absolute deviation (AAD) of the predicted densities from those obtained by the measurements was found to be 0.24%. The proposed PHDC EOS has also been employed for predicting the isothermal compressibility (κT), AAD was found to be 2.43%. This work showed that addition of contributions caused by hard-dimres to PHC model leads to the more accurate results for the density prediction than that previously developed in literature by considering the hard-sphere contribution only. We have also compared the results with other methods when predicting the densities of ILs at elevated pressures.