From Zero Kelvin Upwards: Thermodynamic Modeling of the Mn-Ni System with Third Generation Calphad Models

Accurate thermodynamic prediction at low temperatures presents a significant challenge in solid state physics and materials science. To address this, the third generation Calphad (CALculation of PHAse Diagrams) models are being developed, which enable a physics-based prediction of thermodynamic properties down to zero kelvin. Furthermore, the Inden-Hillert-Xiong (IHX) model, an improved Calphad magnetic model, has been proposed to enhance the modeling accuracy of magnetic transition temperatures and magnetic moments across the entire composition range. The previous assessments of the Mn-Ni system based on the second generation Calphad encountered limitations in reproducing the magnetic properties for the (gamma Mn,Ni) phase, particularly due to the contrasting ferromagnetic behavior on the Ni-rich side and the antiferromagnetic behavior on the Mn-rich side. In this work, the Mn-Ni system was reoptimized on the basis of third generation unary descriptions and Calphad models. To represent the structural characteristics, both the ordered fcc and bcc phases were described by the four-sublattice model for the first time. The obtained thermodynamic parameters result in satisfactory predictions of the phase diagram and thermochemical properties for the Mn-Ni system.