The nuclear spin–spin coupling constants in the water dimer

The nuclear spin–spin coupling constants have been calculated for the water dimer, as well as for the water monomer and dimer surrounded by the dielectric medium. The change due to condensation has been estimated at ∼12 Hz for |J(O–H)| and ∼0.4 Hz for |J(H–H)|. The performance of different basis sets and electron correlation effects, as estimated by the MCSCF wavefunctions, have been investigated. The latter are particularly important for J(H–H). The calculated changes in both J(O–H) and J(H–H) coupling constants are dominated by the Fermi contact and paramagnetic spin–orbital terms.