Symmetric group approach to relativistic CI. III. Matrix elements for spin-dependent operators

Abstract

Matrix element formulas for spin-dependent operators in a basis of spin-adapted antisymmetrized products of orthonormal orbitals (configuration-state functions) are presented. The coefficients of one- and two-electron integrals depend only on the form of the spin-dependence of the operator and on the mutual arrangement of the orbitals which are singly occupied in the pertinent pair of the configuration-state functions. The formulas are useful in implementations of relativistic two-component CI approaches, such as the Pauli CI and projected no-pair CI method. They may be readily used within existing nonrelativistic SGA—CI codes. As examples of applications of the new formulae, spin-own-orbit and scalar spin—spin matrix elements were derived. © 1997 John Wiley & Sons, Inc.