Stability and electronic structure of the magnetic hyperhalogen Fe(BF 4 ) 4

FeCl 4 − and BF 4 − are very stable superhalogen anions, and FeCl 4 − possesses a magnetic moment of 5 μ B due to the singly occupied 3d 5 orbitals of the Fe 3+ . This letter determines the lowest energy structures and stabilities of anionic and neutral Fe(BF 4 ) 4 −/0 and investigates the magnetic hyperhalogen property by using density function theories and configuration interaction method. The binding and dissociation energies indicate that both the anionic and neutral species are stable. The most stable structure of the anion has D 2d symmetry in which the four BF 4 units are coordinated to the central Fe atom in bidentate manner. The vertical and adiabatic detachment energies of Fe(BF 4 ) 4 − reach 10.53 and 9.76 eV, respectively. The 3d orbitals of the central Fe atom form strong covalent bonds with the BF 4 units, and the magnetic moments (5 μ B ) are formed by delocalized spin orbitals. Graphical abstract Magnetic hyperhalogen Fe(BF 4 ) 4 is designed and the lowest energy structures of the anionic and neutral Fe(BF 4 ) 4 -/0 are determined. The binding and dissociation energies show that both the anionic and neutral species have enhanced stabilities. The 3d orbitals of the central Fe atom form strong covalent bonds with the BF 4 units and the anion has a magnetic moment of 5 μB. The most stable structure of the anion has D 2d symmetry with vertical/adiabatic detachment energies 10.53/9.76 eV. The most stable structure of the neutral Fe(BF 4 ) 4 has Cs structure and the corresponding vertical/adiabatic detachment energies are 9.84/8.42 eV.