Ab initio calculations of force fields for H 2CN and C1HCN and vibrational energies of H 2CN

Abstract

Ab initio calculations of electronic energies and fitted force fields are reported for H 2CN and C1HCN. The force field for H 2CN in internal coordinates is used in rigorous, full dimensional variational calculations of numerous vibrational states. The same force field is also used in vibrational self-consistent field (VSCF) calculations, using a new code which is currently restricted to at most four-mode coupling. The convergence of VSCF energies in internal coordinates is examined for one-mode, two-mode, three-mode, and four-mode approximations to the full internal coordinate force field. VSCF calculations using a conventional normal coordinate force field for H 2CN are also reported.