Place: Departmental Lunch Colloquium of the Department of Materials Science and Engineering, Delft University of Technology, Delft, The Netherlands
DFT calculations of several quantities, such as formation enthalpies, have become a standard method in materials science and they are widely applied in thermodynamic modelling and phase diagrams.
In the first part of this talk, a systematic investigation of several binary and some ternary systems of interest for Ni- and Co-based superalloys, based on DFT ground-state calculations at 0K, will be presented. Using the Bragg-Williams approximation, temperaturedependent stable and metastable phase diagrams without adjustable parameters were computed. Features of experimental phase diagrams which are captured in this approach, but also potential pitfalls, will be presented. Benefits for thermodynamic modelling of metastable phases will finally be addressed.
In the second part, DFT-based techniques available to go beyond ground-state calculations and evaluate temperature-dependent effects will be discussed. Results of thermodynamic properties obtained from phonon calculations and electronic excitations in the harmonic and quasi-harmonic approximation. Mechanical instability, found in some of the investigated configurations, and the importance of anharmonic contributions using thermodynamic integration based on Ab Initio Molecular Dynamics (AIMD) is finally discussed.