Bonding Patterns in Intermetallic Compounds

Intermetallic phases have long been among the black sheep in the family of chemical compounds. Their chemical bonding has eluded description by the valence rules, which otherwise are extremely effective. As a result, understanding of the structure–bonding relationships in these phases to date has remained nebulous, even though they form the largest group of inorganic compounds. Their broad industrial applicability and richly varied structural chemistry call for new approaches for explaining their structures, electronic structures, and physical properties. A combination of new experimental and theoretical investigations has revealed interesting local aspects of chemical bonding in metals and thereby pointed to a route from the valence compounds, through the cluster and electron-deficient compounds, to the intermetallic phases.