First principles calculations of structural and defect properties of high-temperature intermetallics

First principles quantum mechanical calculations based on the local-density-functional (LDF) theory have been used to investigate the electronic, structural, and defect properties of transition-metal aluminides and silicides. Three examples are given to show the predictive capability of modern LDF calculation: (1) interfacial properties of two-phase Ti-Al alloys, (2) point defect structure of NiAl and FeAl, and (3) elastic constants and coefficient of thermal expansion (CTE) of Mo5Si3. Emphasis is placed on the effect of interfaces on the planar fault energies in Ti-Al, the interaction between vacancies in B2 aluminides, and the interplay between bonding and the anisotropy in CTE in Mo5Si3. We show that first principles calculation not only yields results in excellent agreement with experiments (if available), but offers information on electronic structure from which a clearer understanding of atomic-level interactions that govern alloy behavior can be made.