Valence correlation in thes2dn,sdn+1, anddn+2states of the firsthyphen;row transition metal atoms

摘要

The major differential valence correlation effects of the lowest lying states arising from thes2dn,sdn+1, anddn+2configurations of the firsthyphen;row transition metal atoms have been characterized using MCSCF and CI procedures. The important correlation effects are found to be, first, angular correlation of the 4s2pair arising because of the near degeneracy of the 4sand 4porbitals and, second, radial correlation of the 3delectron pairs. This large differential radial correlation of the 3delectrons can be interpreted as being due to nonequivalentdorbitals in thesdn+1anddn+2excited states. Both of these effects can be incorporated into a simple MCSCF wave function that reduces the error in the excited state atomic dissociation limits (sim;0.2 eV in Scndash;Cr and sim;0.5 eV in Mnndash;Cu for thesdn+1ndash;s2dnexcitation energy), yet still is of a form which lends itself easily to molecular calculations.