Knowledge Bank

Multiconfiguration self-consistent-field (MCSCF) theory is used to define orbital spaces for the lowest $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma +,3\Sigma +$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi$ states of CaO. First-order type configuration interaction calculations are carried out in these optimized orbital spaces to locate the two lowest energy $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma +$ states, the lowest $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Sigma +$ state and the lowest $\mathrm{<mrow\; data-mjx-texclass="ORD">1,3</mrow>}\Pi$ states. The $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma +$ state is found to be the ground state and lies about 0.4 eV below the $\mathrm{<mrow\; data-mjx-texclass="ORD">1,3</mrow>}\Pi$ states. The reason appears to be the presence of the charge transfer configuration $Ca++O--$ in the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma +$ state. Dipole moments for the $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Sigma +$ and the $\mathrm{<mrow\; data-mjx-texclass="ORD">1,3</mrow>}\Pi$ states are found to be almost linear functions of the internuclear distance, whereas the dipole moments of the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma +$ states are rapidly varying functions of the internuclear distance with values as large as 12 Debyes, Thin will be discussed in terms of a natural orbital population analysis.