Diffusion Monte Carlo simulations of hydrogen fluoride dimers

The diffusion Monte Carlo method is used to simulate vibrational states for HF and DF monomers and dimers. Ground state energies, dissociation energies, and vibrational motions are discussed on the basis of the simulations. Vibrational frequencies for the dimer are calculated using a mean field, local mode analysis, local mode variational calculations, and direct excited state diffusion Monte Carlo simulations. A tunneling splitting calculation is done using a fixed node simulation. Three different potential surfaces are used for the calculations and results are compared with the available experimental data. One of the surfaces is modified on the basis of the calculations to give improved agreement with experiment.