Relationship between Structural Stability and Long-range-order Parameter

The relationship between the structural stability and the long-range-order parameter in the binary alloys is studied using effective atom model based on the pair potential. A analytic equation of the cohesive energy against the long range parameter is given. As a result, the order-disorder transformation of B2 phase is much difficultly to be reached than that of L1₂ phase intrinsically in the same binary alloy system.