Theoretical Study On Magnetic Hyperhalogen Fe（BF₄/AlF₄）₄

There are specific clusters that can mimic the chemical properties of atoms in the periodic table,and these clusters are called"superatoms".Among these superatomic clusters,one of the most widely studied types is superhalogens,which are clusters mimicking the properties of halogens but with electron affinities far exceeding those of halogen atoms.The potential application of superhalogens as building blocks of super-salts,advanced electrolytes in metal-ion batteries,hydrogen storage materials,nonlinear optical materials and multiferroic materials,has attracted considerable interest in the design and synthesis of new superhalogens.In this paper,we designed Fe（BF₄/Al F₄）₄ clusters formed by modifying transition metal Fe atom with superhalogen BF₄/Al F₄ as ligands using spin polarized density functional theories.The binding and dissociation energies ensure the stability of the neutral and anionic Fe（BF₄/Al F₄）₄ clusters.The ADEs/VDEs of Fe（BF₄）₄ and Fe（Al F₄）₄are 9.76/10.53 e V and 9.73/9.76 e V,respectively,which are higher than their superhalogen ligands BF₄（6.90/7.38 e V）and Al F₄（7.70/7.80 e V）,so both Fe（BF₄）₄ and Fe（Al F₄）₄ clusters belong to the category of hyperhalogen.Most of the extra charges in the monoanion Fe（BF₄/Al F₄）₄ clusters are uniformly delocalized the terminal F atoms,which results in the high electron detachment energy.The electronic density of states and molecular orbitals indicate that the 3d orbitals of Fe in the Fe（BF₄）₄^-cluster have a very strong bonding interaction with the B-F bonds,and the 3d orbitals of Fe and the orbital of the BF₄ unit form strong covalent bonds.In the Fe（Al F₄）₄^-cluster,the 3d orbitals of the Fe atom and the 2p orbital of the F atoms have strong bonding interaction,but the orbitals of the Al atoms does not participate.The magnetic moments（5μ_B）of the monoanion Fe（BF₄/Al F₄）₄ clusters are formed by delocalized spins.The dianion Fe（BF₄）₄ cluster with SADEs/SVDEs of 2.20/3.69 e V is a stable dianion,most of the second extra electrons are compensated on the central Fe atom and the bridge F atoms,reducing the repulsion between electrons and thus improving the stability of the cluster.The orbital interactions suggest that the magnetic moment（4μ_B）of Fe（BF₄）₄^2-is formed partly by localized 3d orbitals on Fe atoms and partly by delocalized spins.