Molecular property calculations for excited states using a multireference coupled-cluster approach

In this Letter, we compute the properties of the ground-state and low-lying excited states of the water molecule dominated by quasi-degenerate single-hole–particle-excited determinants with respect to the restricted Hartree–Fock determinant of the ground state. We use an extensively correlated Fock-space-based multireference version of the coupled-cluster (CC) method. The dipole moments of the ground and low-lying vertically excited states of water at the equilibrium geometry have been calculated using the finite-field technique.