This equation can be derived from statistical mechanics. We will do this later on in the course. Recall for now that the van der Waals EOS has two parameters, which in molecular terms is written as where is the excluded volume per molecule, and is a term related to the mean-field potential felt by a central molecule. Many cubic EOS try to improve in some way on the and terms. Higher-order Equations of State.
Cubic equations are inadequate when very high accuracy is required.
Therefore, complex EOS with many parameters have been developed. The MBWR equation of state used here is the same as that used by Nicolas et al . We start by writing the expression for the Helmholtz free energy. These coefficients contain the 32 linear parameters in the MBWR equation. The functions contain exponentials of the density and the one nonlinear parameter.