BASIS SET SUPERPOSITION ERROR EFFECTS ON ELECTRONIC AND NU-FX,NU-F...N STRETCHING MODES OF HYDROGEN-BONDED SYSTEMS FX...NCX (X = H,D)

The FH...NCH hydrogen-bonded complex, which is a reference structure, has been reviewed from an electronic and vibrational point of view. Ab initio calculations have been made, using a large basis set and thus providing first structural and electrical properties on the subunits when the electronic correlation effects are taken into account in very close agreement with the experimental data. The structure and dipole moment of the complex are well represented. The nu(FH) and nu(F...N) stretching modes are calculated by means of the cariational method, taking into account the mechanical anharmonicity and anharmonic coupling between both vibrations. It is shown that the nu(F...N) stretching frequency, which is larger than the experimental value at the self-consistent-field level and especially when electronic correlation effects are taken into account, is strongly decreased, and so approaches the experimental value, when corrected for basis set superposition error.