Knowledge of the thermodynamic, phase equilibria and diffusion properties of potential novel materials can greatly accelerate their development. However, the data needed for new, multi-component materials are often not available.
The CALPHAD (Computer Coupling of Phase Diagrams and thermochemistry) approach allows the development of thermodynamic and diffusion mobility databases enabling the extrapolation of higher systems from binary and ternary systems. Phase equilibria calculations using the thermodynamic databases determine the phases present and compositions, as well as enthalpy contents, temperature and concentration dependence of phase boundaries, and enable the coupling of microscopic and macroscopic models.
Going beyond equilibrium properties, these methods can also be applied to the dynamics of materials. Diffusion rates can be expressed as a product of a thermodynamic factor and diffusion mobility. Diffusion mobility functions are optimized with the CALPHAD method using a variety of diffusion data and a given thermodynamic description. These diffusion mobility databases have become crucial in numerical diffusion process simulations for multi-component alloys where composition and temperature-dependent diffusion-coefficient matrices are needed at each point in the material.