First-order polarization propagator approach to nuclear spin-spin coupling tensors in SiH_4 and AlH_4-.

A first-order polarization propagator approximation has been adopted to compute the full nuclear spin–spin coupling tensors 1J(X–H) and 2J(H–H) in SiH4 and AlH ^- ₄. The higher efficiency of the computational scheme related to the propagator formalism, with respect to the conventional coupled Hartree–Fock method, has been proved. The diamagnetic spin-dipolar term has been found to provide a larger contribution than the Fermi-spin-dipolar cross term to the anisotropy of 1J(X–H). Spin-dipolar contributions are negligible and the bulk of the average coupling is determined by the Fermi contact term.