Electronic Structure of Hf@C28 and Its Ions. 2. CI Calculations

Abstract

Ab initio configuration interaction (CI) calculations were performed on the ground and excited state of Hf@C{sub 28} and its positive and negative ions. Relative core potentials, spin-orbit operators, and symmetry-adapted functions were included in the calculations to take into account the relativistic effects of the heavy atom and to reduce the time and effort of the computation. Double-zeta basis sets were used. Single and double excitations were included in the CI calculations. A number of excitation energies were obtained for Hf@C{sub 28} and its ions. The ground states of Hf@C{sub 28}{sup +}, Hf@C{sub 28}, and Hf@C{sub 28}{sup -} in T{sub d} symmetry were found to be {sup 2}A{sub 1}, {sup 1}A{sub 1}, and {sup 2}E. For Hf@C{sub 28}, values found were the following: ionization potential, 8.08 eV; electron affinity, 0.66 eV; and first excitation energy (to {sup 3}E state), 5. 26 eV. The binding energy for Hf and C{sub 28} to form Hf@C{sub 28} was obtained as 0.71 eV. These results were compared with those from our previous SCF calculations and with experimental data or other theoretical values where available. 27 refs., 2 figs., 7 tabs.