Formulation of the direct configuration interaction method for triplet spin states. Applications to glyoxal Academic Article uri icon

abstract

  • The direct CI method developed by Roos and Siegbahn has been extended to triplet spin states. Included in the CI are all single excitations plus all doubly excited configurations having nonzero Hamiltonian matrix elements with the Hartree-Fock reference configuration. The new method has been implemented as a part of the BERKELEY system of minicomputer-based programs. Applications to the 3Au(n→π*), 3B g(n→π*), and 3B u(π→π*) states of glyoxal (HCO)2 are presented. Some modifications, following Bender's vector method, of the original Roos method for closed-shell singlets are also discussed. These have allowed us to determine fully variational CI wavefunctions including as many as 15 006 configurations (42 456 Slater determinants). © 1978 American Institute of Physics.

author list (cited authors)

  • Lucchese, R. R., & Schaefer, H. F.

citation count

  • 40

publication date

  • January 1978