The State of d Electrons in Transition Metals

This paper gives a brief critique, in elementary language, of the principal types of theoretical pictures which have been advanced concerning the electronic states of transition metals, especially those of the irongroup. It also calls attention to the possibility that some of the properties of these metals can be correlated by the use of concepts which have an exact, not just approximate, meaning for a many-electron system. The Fermi surface is probably a concept of this type. Major conclusions are that in the iron group metalsthe 3d electrons ought not to differ radically from those in the free atoms either in number or in spatial distribution, and that in most, though perhaps not all, of these metals the 3d electrons, magnetic or nonmagnetic,have an itinerant behavior.