Structures and electron affinity of XO₃^0,−, XOF₄^0,− and XO₂F₂^0,− (X = P, As, Sb, Bi): a theoretical study of novel superhalogen formulae and exceptions of superhalogen formulae

Most superhalogen species are in the form of oxides or halides. To enrich the family of superhalogen species, herein, we investigated the structures and electron affinity (EA) values of higher group 15 elements (X = P, As, Sb, Bi) oxyfluoride species XO₃^0,−, XOF₄^0,− and XO₂F₂^0,−, at the CCSD(T)/aug-cc-pVTZ-pp & aug-cc-pVTZ //B3LYP/aug-cc-pVTZ-pp & aug-cc-pVTZ levels (aug-cc-pVTZ-pp for X = Sb and Bi). Some oxyfluoride species, i.e., PO₂F₂^0,−, AsO₂F₂^0,−, SbO₂F₂^0,−, POF₄^0,−, AsOF₄^0,−, SbOF₄^0,− and BiOF₄^0,−, were found to possess higher EA (VDE: 5.0–6.2 eV; ADE: 4.5–5.5 eV) than halogens (F: 3.4 eV; Cl: 3.6 eV). Thus, we recommended that the oxyfluorides in the form of XO₂F₂^0,− and XOF₄^0,− should be considered as potential superhalogens, which have not been considered previously. Surprisingly, we showed that BiO₃ and BiO₂F₂, in superhalogen formulae, possess a high vertical detachment energy (VDE) yet a low adiabatic detachment energy (ADE). This is in marked contrast to the previously reported superhalogens, which generally contain both the high VDE and high ADE values. It is the first report about exceptions of superhalogen formulae. These findings revealed that for the analogous main-group compounds with the same structural formula, the difference in the metallic property of the core element could lead to the significant difference in the ground structures of either the anionic or neutral structures, which would result in the much differed superhalogen features.