Second nearest-neighbor interactions in ternary regular solutions
The concept of classical regular solutions has been expanded by considering both first and second nearest-neighbor interactions between randomly distributed molecules. While the present model requires an ideal entropy of mixing, as does the classic regularity model, its heat of mixing is expressed by a more flexible equation which attributes the second-order terms of the Margules formalism to first nearest-neighbor interactions, and the third-order terms to second nearest-neighbor interactions. The activity–composition relations have been expressed by a single equation of the grand partition function, which converges to that of the classical regularity with decreasing contributions from second nearest-neighbor molecules.