VIBRATIONAL AND THERMAL AVERAGING OF THE INDIRECT NUCLEAR SPIN-SPIN COUPLING-CONSTANTS OF CH4, SIH4, GEH4 AND SNH4

The effects of nuclear motion on the indirect nuclear spin-spin coupli ng constants of CH4, SiH4, GeH4 and SnH4 were calculated up to first o rder in the normal coordinates. We report the random-phase approximati on, multiconfigurational linear response and second-order polarization propagator calculations of the zero-point rovibrational corrections, as well as the temperature dependence of both one-bond and two-bond co upling constants. We find that the random-phase approximation overesti mates the zero-point corrections. The results demonstrate that rovibra tional corrections are as important as the non-contact terms and must be included in accurate determinations of indirect nuclear spin-spin c oupling constants of these molecules.