Determining the bonding in intermetallics using electron energy loss spectroscopy and density functional theory

The use of many intermetallics is limited by their brittleness at room temperature. This brittleness may be due to a number of factors, one of which may be a covalent component to the bonding which influences dislocation mobility. In order to understand and improve the mechanical properties of intermetallics it is therefore important to characterise the nature of the bonding. Electron energy loss spectroscopy (EELS) and density functional theory have been used to study the bonding in NiAl, FeAl, CoAl and nonstoichiometric NiAl. It is shown that there is a covalent component to the bond between the transition metal atom and the nearest neighbour Al atom. Deviations from stoichiometry in NiAl are also discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.