Many-Body Theory for Hyperfine Fields in Iron-Group Ions—Ferric Ion

Abstract
The hyperfine constant of Fe+3 ion is calculated by the linked-cluster many-body theory procedure. The first-order contribution representing exchange-core-polarization (ECP) effect leads to a hyperfine constant of - 45.46 MHz. Electron-electron interaction effects involving both consistency and correlation contribution are found to be about 12% of the ECP effect. Comparison is made with experimental hyperfine fields in solid state from Mössbauer studies, and the relative importance of covalency effects as compared to electron-electron interaction effects on the hyperfine constant are discussed.