Prediction and characterization of a new kind of alkali–superhalogen species with considerable stability: MBeX3 (M = Li, Na; X = F, Cl, Br)

Abstract

The geometries of the MBeX₃ (M = Li, Na; X = F, Cl, Br) series with all real frequencies are reported using the B3LYP and MP2 methods with the 6-311+G(d) basis set. The natural bond orbital (NBO) and atom in molecule (AIM) analyses indicate the ionic character of the M–X bonds connecting the alkali atom M and the superhalogen BeX₃. The introduction of a counterion M⁺ only slightly affects the geometry of BeX₃⁻, but produces a more stable species. The bond energies (E_b) and vertical ionization potentials (VIP) of the MBeX₃ species are obtained at the CCSD(T)/6-311+G(3df) level. These alkali–superhalogen species exhibit large E_b (130.4–222.3 kcal mol⁻¹) and VIP values (9.46–14.05 eV) to show considerable stabilities. In addition, both E_bs and VIPs of MBeX₃ are found to be closely related to the electronegativity of the X ligands and partial atomic charges.