Estimation of Critical Parameters from Quantum Mechanics

This chapter discusses the estimation of critical parameters from quantum mechanics. The QSPR method combined with multiple linear regression is an efficient and elegant way to estimate from scratch the critical parameters of a wide range of compounds. Calculated critical parameters for pure compounds including extrapolation to the limit of extended systems are both in agreement with experimental data and values obtained by group contribution methods, though, in some cases, these contribution methods are unable to correctly describe the saturation behavior of critical temperature. To obtain the critical parameters for binary mixture, the Redlich's logarithmic-hyperbolic interpolation functions have been used. The great advantage of this method is that only critical parameters of pure compounds are required. Two mixtures have been studied butane-hexane, C0 2 -pentane. Calculated mixture critical values are in very good agreement with experimental data, illustrating that the combination of empirical rules and QM is possible and often valuable when carefully performed.