ENGEL-BREWER ELECTRON CORRELATION MODEL - A CRITICAL DISCUSSION AND REVISION OF CONCEPTS

A critical review of the Engel-Brewer theory of metallic bonding is pr esented with an emphasis on its inapplicability to transition metals. Taking recourse to pseudopotential arguments for nontransition metals and to tight binding model for d-transition metals, the cohesive and c rystal structure trends among metals across the periodic table is brie fly discussed. It is clear that a direct inclusion of d-electron count s is absolutely necessary to correlate meaningfully the observed struc tural trend with the valence electron configuration. In view of this l imitation, the classical Brewer's scheme is revised in such a manner t hat some of the anomalies encountered in the case of transition metals are removed. A discussion of the philosophical basis of Brewer's mode l is presented.