Electronic Structure and Charge Transfer in CoAl

Self-consistent APW band calculation has been performed for the intermetallic compound CoAl having the CsCl-type structure. The resulting density of states, partial densities of states, and Fermi surface are found to be favorably compared with the experimental values of electronic specific heat, Pauli susceptibility, X-ray emission spectroscopy, and Knight shift. Charge transfer has been related with the electrostatic Ewald potential felt by an electron in the interstitial region between atoms. This treatment has an advantage that the atomic volume is not necessary to be determined. The amount of charge transfer from aluminum to cobalt has been estimated to be 0.283. It has been found that the region delineated by the position of the maximum potential is electrically neutralized by the nuclear charge and the surrouning electrons, and has a close connection with the atomic size in the compound. The relation between the neutralized and the atomic volume is discussed.