AN ITERATIVE DIFFERENCE-DEDICATED CONFIGURATION-INTERACTION - PROPOSAL AND TEST STUDIES

An earlier work proposed a difference-dedicated configuration interact ion method based on effective Hamiltonian arguments and was essentiall y devoted to the calculation of transition energies and binding energi es. Using the resulting density matrices, the procedure may be made in dependent of the choice of starting molecular orbitals. This iterative redefinition of the MOs improves the quality of the results, as shown by comparing to full-CI results on CH2, CH2+ and SiH2 vertical and ad iabatic transition energies. The efficiency of the method for the trea tment of weakly avoided crossings and for the determination of binding energies is illustrated on the LiF molecule. The mean deviation of th e iterative difference-dedicated CI results to FCI energy differences is lower than 0.1 eV.