Statistical thermodynamics of long-range order are part of the Bureau of Mines program to provide a scientific base for use in developing new alloys and alloy phases. Numerous statistical thermodynamic attempts have been made to formulate the behavior of long-range order in alloys after the work of gorsky, and bragg and williams (gbw). The quasichemical method is often erroneously claimed to be an improvement over the gbw method. The permutation of the bonds in the quasichemical method is made to become the permutation of atoms for zero exchange energy, or when the temperature is sufficiently high, through a dubious normalization process. The normalization process of the quasichemical method yields the same equations for the excess Gibbs energy of solution as without normalization, and the actual enumerations of configurations prove that the permutable entities are the atoms, not the bonds. This communication has a twofold purpose: (1) to show that the permutation of atoms yields proper new equations for order-disorder phenomena after reasonable corrections and (2) to discuss the errors in the previous regular assembly treatments.
Scr. Met., V. 17, No. 1, 1983, PP. 53-58