Formation and properties of iron-based magnetic superhalogens: A theoretical study

Abstract

In order to explore new magnetic superhalogens, we have systematically investigated the structures, electrophilic properties, stabilities, magnetic properties, and fragmentation channels of neutral and anionic Fe(m)F(n) (m = 1, 2; n = 1-7) clusters using density functional theory. Our results show that a maximum of six F atoms can be bound atomically to one Fe atom, and the Fe-Fe bonding is not preferred in Fe2F(n)(0/-) clusters. The computed electron affinities (EAs) indicate that FeF(n) with n ≥ 3 are superhalogens, while Fe2F(n) can be classified as superhalogens for n ≥ 5. To further understand their superhalogen characteristic, the natural population analysis charge distribution and the HOMOs of anionic clusters were also analyzed. When the extra negative charge and the content of HOMO are mainly located on F atoms, the clusters could be classified as superhalogens with EAs substantially surpass that of Cl. By calculating the binding energies per atom and the HOMO-LUMO gaps, FeF3, FeF4(-), Fe2F4, Fe2F5(-), and Fe2F7(-) clusters were found to have higher stabilities, corresponding to the Fe atoms that are attained at their favorite +2 and +3 oxidation states. Furthermore, we also predicted the most preferred fragmentation channel and product for all the ground state clusters. Even more striking is the fact that both neutral and anionic Fe(m)F(n) (m = 1, 2; n = 1-7) clusters carry large magnetic moments which mainly come from 3d orbital of iron atom.

Are superhalogens without halogen ligand capable of transcending traditional halogen-based superhalogens? Ab initio case study of binuclear anions based on pseudohalogen ligand

“…5,[10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] Along with the deepening of the related researches, it has been a Author to whom correspondence should be addressed. Electronic mail: rayinyin@nwu.edu.…”

Theoretical Search for an Iron‐Based Magnetic Superhalogen with Halogen or Interhalogen as Ligand

“…The most abundant oxidation states of it are +2 and +3, but higher oxidation numbers up to +6 are experimentally known. [42] Inspired by these results, our group [43] has performed an investigation on the iron-fluorine clusters to explore new magnetic superhalogens. After a systematic study, we think it is better to let the central transition metal atoms be at or over their favorite oxidation, so that the magnetic superhalogens can possess high electron affinity.…”

“…[ 43] This might be due to the fact that the electronegativity of F (3.98) is much larger than that of Cl (3.16) and Br (2.96), and the atomic radius of F is smaller than those of Cl and Br. Therefore, the fluorine has a stronger ability to attract the electrons of iron, thereby resulting in a higher oxidation state of Fe.…”

“…This further confirms our previous deduction. [43] When one tries to synthesize new magnetic superhalogens with transition-metal atoms, it is better to let the central metal atoms reach or exceed their favorite oxidation state and the number of halogen atoms should exceed the preferred formal valence of the metal atom.…”

Polynuclear Li12F13 − anion as a steric shielding agent with respect to selected metal ions

“…Since then, many other superhalogen anions [e.g., Na k Cl − k+1 (k = 1-4) and MX 3 − (where M = Be, Mg, Ca; X = Cl, Br)] have also been identified experimentally [9,10]. As indicated by both theoretical predictions and experimental measurements, the original superhalogen formula (MX k+1 ) can be extended to include the polynuclear M n X nk+1 neutral superhalogen compounds (containing n central atoms) whose corresponding polynuclear M n X − nk+1 anions exhibit even larger electron binding energies than their mononuclear counterparts [11][12][13][14][15][16][17]. In addition to numerous applications of superhalogens, we have recently pointed out their possible usage as strong oxidizing agents [18][19][20][21] and Lewis-Brønsted superacid precursors [7,22, 23].…”