General form of the cross-energy parameter of equations of state

Phase equilibrium calculations with cubic equations of state are sensitive to mixing and combining rules employed. In this work, we present a suitable general form of the combining rule for the cross-energy parameter, often c onsidered to be the key property in phase equilibrium calculations. The pro posed rule is derived from molecular considerations, namely, the London-Mie theory. The typically used geometric mean (GM) and other combining rules c an be deducted from this expression from different values of the parameter n, which is the attractive tail of the Mie potential. We show that using th is n parameter as the variable instead of the commonly employed k(ij) offer s useful insight into the behavior of cubic equations of state for a large number of asymmetric systems including gas/alkanes, polymer solutions and b lends, and alcohol/alkane and gas/solid systems.