Modelling at the atomic scale of ternary iron-based alloys of technological interest, such as FeCrNi, FeCuC, FeNiMn, FeCrW and FeCrMo. A study within density functional theory of the interaction between point defects and soluted atoms, extended to thermodynamical properties. Derivation of interatomic potentials consistent with DFT energetics and phase stability indications, as well as experimental phase diagram data.