Understanding and controlling the thermodynamic behavior of molten fluoride salts is critical for their deployment in advanced energy systems, including molten salt reactors. Self-consistent Gibbs energy functions were developed to describe the thermochemical behavior of the fission product SmF3 with LiF, NaF, and KF using the modified quasi-chemical model in the quadruplet approximation. Enthalpies of mixing for each pseudobinary system were estimated through a correlative method based on the i