On the extent of intramolecular hydrogen bonding in gas-phase and hydrated 1,2-ethanediol.

We investigate the quantum dynamical nature of hydrogen bonding in 1,2-ethanediol and monohydrated 1,2-ethanediol using different levels of ab initio theory. Global full-dimensional potential energy surfaces were constructed from PW91/cc-pVDZ, B3LYP/cc-pVDZ, and MP2/cc-pVDZ ab initio data for gas-phase and monohydrated 1,2-ethanediol, using a modified Shepard interpolation scheme. Zero-point energies and nuclear vibrational wave functions were calculated on these surfaces using the quantum diffusion Monte Carlo algorithm. The nature of intra- and intermolecular hydrogen bonding in these molecules was investigated by considering a ground-state nuclear vibrational wavefunction with reduced complete nuclear permutation and inversion (CNPI) symmetry. Separate wavefunction histograms were determined from the ground-state nuclear vibrational wavefunction by projection into bondlength coordinates. The O−H and O−O wavefunction histograms and vibrationally averaged distances were then used to probe the extent of i...