Bonding mechanisms in γ-TiAl: Comparison between absorption near edge fine structures and theoretical predictions

Abstract

The near edge fine structures of the γ-TiAl alloy recorded either in XAS (K edges) or in EELS (L edges) have been compared with calculations based on band structure or full multiple scattering techniques. Good agreement between experiment and theory has been achieved for the Ti-K, Al-K and Al-L edges. The discrepancy observed between experiment and theory at the Ti-L₂₃ edges is interpreted as the failure of the single particle approximation at these edges due to core hole and strong exchange interaction. Strong hybridization between the Ti and Al atoms is demonstrated and supported by analysing charge density maps obtained from the band structure calculations. The existence of Ti-d-Al-p, Ti-d-Al-s and Ti-d-Ti-d hybrids, and therefore covalent character in the bonding, are discussed in terms of the mechanical properties of the γ-TiAl alloy.