Electric Dipole Moment of Diatomic Molecules by Configuration Interaction. IV. Basis Set Dependence in CO a3Φ

Abstract

The effect of basis set quality on configuration interaction wavefunctions is considered theoretically. In particular, one‐electron operator properties and basis sets not too far from the Hartree‐Fock limit are considered. It is then shown that a CI function will contain essentially the same error due to basis set as the SCF function upon which it is based. This result is used to account for the error in a previously reported dipole moment calculation on CO a³Φ; starting from an SCF function with an energy 0.009 a.u. and a dipole 0.16 D above the Hartree‐Fock limit, a CI dipole of 1.55 D was obtained. Using a larger basis set, an improved SCF function is presented which has an energy only 0.001 a.u. and a dipole 0.04 D above the HF limit. A CI function based on this SCF gives a dipole moment of 1.43 D, which may be compared with the experimental value of 1.37 D.