Thermodynamics permeates all the scales providing a natural link between fundamental materials science and engineering methods. Enthalpies of formation, for instance, can be calculated by first-principles density functional theory and can also be measured. Both methods provide discrete values. The use of that information in applications requires a model which describes the behavior of these quantities as a function of temperature, composition and pressure as well as a consistent link to other properties. The CALPHAD method is used in the project group to model Gibbs energies and its derivatives for stable and metastable phases providing the possibility of interpolations and extrapolations into not measured or fundamentally calculated states. It allows the calculation of single phase properties as well as the relative stability of competing phases as function of temperature, composition and pressure.

Discussion of the project group during
the ICAMS Scientific Retreat 2011.

First-principles calculated energies of formation are used as input for thermodynamic models that are able to calculate enthalpies, entropies and Gibbs energies. The thermodynamic database can also be trained using experimental data. The databases are then used, for example, to calculate solid/liquid fractions which in turn are employed in phase-field simulations of microstructure evolution.