Ab initio characterization of XH3 (X=N,P). I. Ammonia, phosphine, and their related ions and radicals: structure and thermochemistry

Ammonia, phosphine and their related cations, anions and radicals have been investigated at a high level of accuracy. The singles and doubles coupled cluster method including a perturbational correction for connected triple excitations, CCSD(T), in conjunction with correlation consistent basis sets ranging in size from triple to sextuple zeta have been employed. Extrapolation to the complete basis set limit has been used with accurate treatments of core– valence correlation effects in order to accurately predict structures, ionization potentials, electron affinities as well as N–H and P–H bond dissociation energies. For all the species studied, harmonic vibrational frequencies have also been evaluated in order to obtain zero-point corrections.