CALCULATION OF ELECTRONIC STATES OF LI2+ AS A FREE ION AND IN A POINT-ION LATTICE

Electronic structures for the Li2+ molecule ion have been calculated using Hartree-Fock-Roothaan methods. Ground-state and several excited-state energies have been obtained for various internuclear distances for the Li2+ as both a free ion and as a substitutional defect in a point-ion crystal lattice. The present calculation gives a ground-state binding energy for the free ion of 1.24 eV, which is in agreement with a calculation by James. In a crystal-lattice environment, equilibrium internuclear distances are about 4.0 a.u. for the ground and the first few excited states, with a transition energy of no more than 0.9 eV for the first allowed transition. These results do not support the suggestion by Farge that the optical-absorption peak at 2.25 eV and the associated fluorescence at 1.36 eV, observed in irradiated LiF, are due to the Li2+ defect. © 1969 The American Physical Society.