GAUSSIAN DENSITY FUNCTIONAL CALCULATIONS ON HYDROGEN-BONDED SYSTEMS

As a test of the applicability of the density functional theory to systems containing hydrogen bonds, linear combination of Gaussian type orbitals-local density calculations have been performed on two intermolecular and two intramolecular hydrogen-bonded systems. A comparison is made of results using the local density approximation (LDA) and those including nonlocal density gradient type corrections, using two different nonlocal functionals. The calculated minimum energy structures for the water dimer and the formamide-water complex are presented. The binding energies calculated for these systems, including a treatment of the basis set superposition error using the counterpoise method, are also presented. For the water dimer, the calculated harmonic frequencies and intensities are reported, and their shifts with respect to those of the water molecule are discussed. The minimum energy structures and calculated vibrational frequencies are reported for malonaldehyde and glyoxylic acid. Overall, the LDA is found to be seriously deficient. The nonlocal corrections provide encouraging improvement.