ELECTRONIC-STRUCTURE AND MECHANICAL-BEHAVIOR OF TRANSITION-METAL ALUMINIDES - A 1ST-PRINCIPLES TOTAL-ENERGY INVESTIGATION

First-principles quantum mechanical calculations based on the local-density-functional theory have been used together with the anisotropic elasticity theory of dislocations to study the electronic and mechanical properties of transition-metal aluminides. The bonding mechanism can be described by the combination of Al-to-transition metal charge transfer and strong p-d bonding hybridization effects. Point defect self-energies, elastic constants, various shear fault energies, and cleavage energies are determined from first-principles for the L1(2) (Ni3Al and trialuminides), B2 (FeAl and NiAl), and L1(0) (TiAl) structure-base intermetallics. A comprehensive understanding of the bonding mechanism, point defect structure, yield strength anomaly, and brittle fracture behavior forms the basis for a better assessment of extrinsic effects on the strength and ductility of aluminides (e.g., hydrogen in FeAl, and boron in Ni3Al).