DENSITY FUNCTIONAL-STUDY OF A HIGHLY CORRELATED MOLECULE, FOOF

The molecular and electronic structure of FOOF has been calculated in the density functional framework with both numerical and Gaussian basis sets. The geometry is well predicted by the local density functional method with the O-O bond length calculated to better than 0.01 angstrom and the O-F bond length to better than 0.015 angstrom. The predicted vibrational frequencies are in reasonable agreement with experiment with the frequencies all greater than the experimental values. The largest error in the calculated frequencies is found for the symmetric O-O-F bend, which is predicted to be about 20% too large. An analysis of the force constants in terms of simple internal coordinates reveals large couplings between the stretches. The rotational barriers are calculated and shown to be larger than the dissociation energy leading to loss of F. The computed dissociation energies for loss of one and two F atoms are found to be larger than the experimental values. Whereas geometries and frequencies are well described within the local density approximation, inclusion of nonlocal corrections is required for the dissociation energies to have even qualitative agreement with experiment.