Analysis of EELS near edge structures to study the bonding character in intermetallic alloys

The energy loss near edge structures of an early transition metal aluminide (TiAl) and late transition metal aluminides (FeAl and NiAl) have been compared with calculations based on band structure techniques. The differences between theory and experiment are discussed in terms of the validity of the single particle approximation. The better agreement between experiment and theory for the late transition metal aluminides is attributed to the screening of the core hole and limited exchange interaction. Strong hybridisation between the transition metal and Al atoms is demonstrated and anisotropy in the energy loss spectra of TiAl is presented. These bonding characteristics are discussed in terms of differences in the crystal structures, valence charge density maps and properties.