Structural stability of alloys : ab initio and phenomenology

The prediction of phase stability trends and phase diagrams of multi-component complex alloys is undoubtedly the Holy Grail of alloy physics and materials properties simulation. First-principles results of alloy energetics and phase diagrams can appropriately supplement thermodynamic databases that are used within the phenomenological CALPHAD approach for predicting the stability properties of complex multi-component alloys. Routine energy minimization of alloys stability within ab initio methodology provides input to CALPHAD in terms of heats of formation and transformation for alloys exhibiting various crystalline structures and any chemical configuration. Additionally, ab initio energetics combined with a statistical treatment provides the necessary thermodynamic information for subsequent assessments similar to those performed with experimental data within CALPHAD. Following an overview of the first-principles and phenomenological methodologies, examples of both aspects of the interfacing will be presented with applications to multi-component alloys. Validity of this interfacing and its relevance to alloy design will be discussed. Finally the usage of these results in meso-scale modeling of microstructure evolution will be discussed. Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.