Thermodynamic modelling of LiF–LnF3 and LiF–AnF3 phase diagrams

The phase diagrams of the LiF–LnF3 series, where Ln = La–Sm, and of LiF–AnF3, where An = U, Pu, have been optimized using Redlich–Kister functions. The phase diagrams of LiF–AmF3 and LiF–PuF3–AmF3 have been calculated. The necessary Gibbs energy functions for americium trifluoride were defined by use of a semi-empirical method. The excess Gibbs energy terms, which are expressed as Redlich–Kister polynomials and describe the effect of interaction between the two fluoride components in the liquid phase, were obtained by translating the trends observed in the lanthanide trifluoride series into the actinide series. A single eutectic has been found in the LiF–AmF3 system with the eutectic point at ≃33 mole% AmF3 and at ≃951 K.