Interatomic potentials consistent with thermodynamics

A desirable property of interatomic potentials for atomistic simulations of microstructure evolution under irradiation is consistency with the experimental phase diagram. A methodology to fit semi-empirical potentials with this goal in mind, developed by the authors, is reviewed and discussed. The methodology is based on the coupling of the Cluster Variation Method technique, using the correlation function formalism to express energy and entropy, to other, more standard requirements. The method has been succesfully applied to the construction of an embedded-atom method (EAM) many-body potential for the FeCu system, a prototype alloy for the understanding of reactor pressure vessel steels embrittlement under irradiation. Efforts to apply a similar methodology to more challenging systems (FeCr, FeNi) required the adoption of more flexible fitting techniques, which are here discussed.