Ab initio studies on ONH3, ONF3 and OCF 3 − , using polarization functions and configuration interaction methods

SCF geometry optimizations, using double-zeta basis sets with polarization functions, either as d-orbitals or bond functions, were performed on ONH₃, ONF₃, and OCF ₃ ^? . The bonding in these molecules is discussed with the help of orbital density plots and Mulliken population analyses. ONF₃ can be explained as donor-acceptor product of O with NF₃. For OCF ₃ ^? , diffuse functions have also been added to the basis set. The CF distance is predicted to be 1.39 Å, in qualitative agreement with the known infrared spectrum. With the best basis set, the NF distance of ONF₃ is too short by 0.08 Å at the SCF level. A geometry optimization by the configuration-interaction method gives the NF distance as well as the ON distance in excellent agreement with experimental results.