Electric Dipole Moment of Diatomic Molecules by Configuration Interaction. IV. Basis Set Dependence in COa3PHgr;

摘要

The effect of basis set quality on configuration interaction wavefunctions is considered theoretically. In particular, onehyphen;electron operator properties and basis sets not too far from the Hartreehyphen;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 COa3PHgr;; starting from an SCF function with an energy 0.009 a.u. and a dipole 0.16 D above the Hartreehyphen;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.