Properties of valuable new intermetallics: Brewer–Engel model applied to the bonding of transition metal dialuminides

The Brewer–Engel Theory is a model capable of predicting novel materials, used in the past in particular for quite stable intermetallics based on the reaction of metals with non-bonding d electron pairs combined with metals with empty d orbitals. In this paper are shown the calculation procedures for bonding energies of 1:2 transition metal aluminide compounds characterized by MgCu2 crystal structures. The model utilizes parameters that include crystal field effect, Hume-Rothery Rules, and a modified Born–Haber cycle to characterize covalent and ionic bonding contribution of alloys. Interactions between transition metals exhibit enhanced d-bonding, whereas interactions between transition metals and non-transition metals exhibit reduced d-bonding. From the bonding energies, the percentage ionicity factor is determined which is an indication of the stability of the intermetallic compound.