Analysis of Electronic Structures and Chemical Bonding of Metal‐rich Compounds. 2. Presence of Dimer (T–T)4–and Isolated T2–Anions in the Polar Intermetallic Cr5B3‐Type Compounds AE5T3(AE= Ca, Sr; T= Au, Ag, Hg, Cd, Zn)

First principles density functional calculations were carried out to probe the oxidation states of the transition‐metal and alkaline‐earth elements in the Cr5B3‐type compounds AE5T3consisting of T2dimers and isolated Tatoms (i.e., Ca5Au3, Ca5Ag3, Ca5Hg3, Sr5Cd3, and Ca5Zn3). The electronic structures of all these AE5T3compounds are best described as [(AE2+)5(T–T)4–(T2–)]+4e–. In the covalent bonding of the AE2+ions with the transition metal anions T2–, the (n–1)d orbitals of AE2+contribute more than the ns and np orbitals of AE2+.