Electric Dipole Moment of Diatomic Molecules by Configuration Interaction. I. Closed-Shell Molecules

A scheme has been developed for selecting a manageable number of configurations (less than 200) to be used in a configuration interaction calculation to obtain the electric dipole moments of closed‐shell diatomic molecules. Calculations have been performed on LiH ${\mathrm{(R}}_e\text{\hspace{0.17em}=\hspace{0.17em}3.015}\mathrm{a.u.})$ , CO ($R_e\text{\hspace{0.17em}=\hspace{0.17em}2.132}\mathrm{a.u.}$ and $\text{R\hspace{0.17em}=\hspace{0.17em}2.2853}\mathrm{a.u.}$ ), CS ${\mathrm{(R}}_e\text{\hspace{0.17em}=\hspace{0.17em}2.89964}\mathrm{a.u.})$ , and NaLi $\text{(R\hspace{0.17em}=\hspace{0.17em}5.5}\mathrm{a.u.})$ . A dramatic improvement over the restricted Hartree–Fock value is obtained. At $R_e$ the RHF, CI, and experimental dipole moments (in debye) are LiH: 6.00, 5.86, 5.83; CO: − 0.27, 0.12, 0.11; and CS: 1.56, 2.03, 1.97.