Order-disorder or phase-separation transition: Analysis of the Au-Pd system by the effective site energy model

F. Berthier, J. Creuze, T. Gabard, B. Legrand, M.-C. Marinica, C. Mottet
2019 Physical review B  
Using a many-body interatomic potential for the Au-Pd system, we determine a bulk phase diagram which presents unexpected characteristics for a system with ordering tendency. Indeed, this system displays a miscibility gap between pure Pd and Au c Pd 1−c (with c ≈ 0.2) beyond the order/disorder critical temperature of the AuPd 3 compound. Enthalpic and entropic contributions of the permutation free energy are determined via Monte Carlo simulations, in particular the vibrational entropy, which is
more » ... in good agreement with direct calculation. Finally, the effective site energy model, recently developed to describe the thermodynamical forces driving the bulk phase diagram, is used to demonstrate that the miscibility gap in the Au-Pd system comes from competition between elastic and chemical effects.
doi:10.1103/physrevb.99.014108 fatcat:vgjbnzpl4ffnphqqmtz5he6beu