AB-INITIO MO STUDIES OF NUCLEAR SPIN-SPIN COUPLING-CONSTANTS IN CH4, SIH4, ALH4- AND GEH4 SYSTEMS

Ab initio molecular orbital calculations of electron coupled nuclear spin-spin coupling constants are performed for CH4, SiH4, AlH4- and GeH4 systems using the SCF perturbation theory. Basis set dependence of the major contributing terms such as orbital diamagnetic, orbital paramagnetic, spin dipolar and Fermi contact terms are studied. The study also illustrates the relative importance of bend centred functions and nuclear centred polarization functions in predicting the directly bonded and geminal couplings in the systems selected. Basis sets having uncontracted core s functions and augmented with bond functions seem to predict most of these couplings fairly satisfactorily when compared to the experimental values.