Knowledge Bank

This work discusses the results of Hartree--Fock studies of the isoelectronic ions $(CO2)2\mathrm{<mrow\; data-mjx-texclass="ORD">-</mrow>}$ and $(NO2)2\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$. Three types of structures are examined for each of these species: $D2h$ and $D2d$ structures with the odd electron symmetrically shared between the monomer units and $Cs$ structures in which the odd electron is essentially localized on one of the monomer units. For both ions the equilibrium structures are predicted to be of the $Cs$ form for $(CO2)2\mathrm{<mrow\; data-mjx-texclass="ORD">-</mrow>}$ and $(NO2)2\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ the $Cs$ structures are predicted to be more stable than the $D2h$ structures by 0.2 and 1.6 eV, respectively. Moreover, the ions in their $Cs$ structures are well described as $CO2\cdot CO2\mathrm{<mrow\; data-mjx-texclass="ORD">-</mrow>}$ and $NO2\cdot$ $NO2+$, that is as monomeric ions ``solvated’’ by neutral monomers. The bonding in the $Cs$ structures is compared to that of the $D2h$ and $D2d$ species. Preliminary results are also presented for the $(BeF2)2-$ and $(N2O)2\mathrm{<mrow\; data-mjx-texclass="ORD">-</mrow>}$ ions.