Theoretical calculation of vertical ionization potentials of B2H6 by means of ΔESCF procedures

The vertical ionization potentials (IPS ) of B₂H₆ are calculated by means of the ΔE_SCF procedure, within the scheme of ab initio LCAO-MO-HF-SCF . The basis set used is LEMAO -3G. The scaling factors of the various atomic orbitals for the ground state and for the various hole states are optimized independently. The iteration procedure is specially designed to avoid the changes of the symmetry of the remaining occupied orbitals. The 1 ag (B1s) hole is found to be localized. The vertical IP of the 1 ag electron is calculated to be 196.5 eV, in fair agreement with experimental value. The D_2h symmetry is thereby broken and reduced to C_2V symmetry. The valence holes are found to be delocalized. The calculated vertical IPS are: 21.781, 16.974, 14.842, 14.389, 13.599, and 12.380 eV for the 2ag, 2b1u, 1b3u, 1b2u, 3ag, and 1b3g electrons, respectively. The agreement with experimental values is much better than the Koopmans' values. All these results are in favor of the concept that the nature of the convelent bond should be considered as a result of the mutual interactions and mutual conditioning between the wave nature of the electronic motion on the one side and the various attractive and repulsive factors on the other side.