Multiconfigurational Hartreendash;Fock studies of avoided curve crossing using the Newtonndash;Raphson technique

摘要

A mode controlling scheme for use in second order Newtonndash;Raphson multiconfigurational Hartreendash;Fock calculations has been developed and applied on the avoided curve crossing for the lowest three states of4Pgr; symmetry of BO and on the valencehyphen;Rydberg mixing in the lowest two states of3Sgr;minus;usymmetry in O2. Convergence of the multiconfigurational Hartreendash;Fock calculations was easily obtained in all calculations, even where roothyphen;flipping occurred. We further demonstrate how an MCSCF calculation may occasionally be reparametrized, that is, the same MCSCF total energy may be obtained using two different sets of configuration lists. One parameter list may give roothyphen;flipping, whereas another parameterization may not. This is exemplified in a calculation on theEthinsp;3Sgr;minus;ustate of O2at 2.13 a.u..