Enthalpy of mixing for ternary fcc solid solutions from special quasirandom structures

Enthalpies of mixing for ternary fcc solid solutions in Al–Cu–Mg, Al–Cu–Si, and Al–Mg–Si systems are calculated from first-principles study of ternary fcc Special Quasirandom Structures (SQS) whose correlation functions are close to those of completely random fcc solid solutions. It is shown that ternary fcc SQSs calculations at four different compositions in each system, i.e.  x A = x B = x C = 1 3 ; x A = 1 2 , x B = x C = 1 4 ; x A = 1 4 , x B = 1 2 , x C = 1 4 ; and x A = x B = 1 4 , x C = 1 2 , can be used to determine whether the extrapolated enthalpy of mixing from corresponding three binaries is able to describe the ternary mixing behavior correctly.