Theoretical search for small linear doubly charged anions

The electronic stabilities of linear diatomic C22−, BN2−, BP2−, BeO2−, BeS2−, MgO2−, MgS2−, O22−, SO2−, and S22−; triatomic NCN2−, SBN2−, OBeO2−, SBeC2−, SBeO2−, OMgO2−, SMgS2−, PCP2−, and SCC2−; tetratomic OCCO2− and SCCS2−; and pentatomic Be2O32−, Be2S32−, Mg2O32−, and Mg2S32− dianions were studied at the Hartree–Fock level with Gaussian basis sets including diffuse and polarization functions, as well as at the second-order Mo/ller–Plesset level. Vertical first detachment energies of several dianions were also calculated at the fourth-order Mo/ller–Plesset level. All diatomic, triatomic, and tetratomic dianions were found to be unstable to electron loss. The pentatomic Mg2S32− dianion is predicted to be stable to electron loss with an electron detachment energy of 0.2 eV. This species is likely to be the smallest electronically stable linear dianion.