USE OF MOLECULAR-DYNAMICS SIMULATIONS WITH AB-INITIO SCF CALCULATIONSFOR THE DETERMINATION OF THE DEUTERIUM QUADRUPOLE COUPLING-CONSTANT IN LIQUID WATER AND BOND LENGTHS IN ICE

The deuterium quadrupole coupling constant and asymmetry parameter in heavy water were determined using ab initio SCF calculations. Snapshot s from a molecular dynamics simulation were used to give liquid water cluster configurations and the influence of simulation parameters on t he quadrupole coupling constant was investigated. The electronic poten tial model and the number of molecules in the molecular dynamics simul ation and the pressure of the system were found to have only a small i nfluence on the quadrupole coupling constant. The average value of the quadrupole coupling constant at room temperature, corrected for the k nown deficiency of the ab initio calculation in the gas phase, yields a quadrupole coupling constant of 253 kHz, in perfect agreement with t he most recent experiments. The oxygen-deuterium bond lengths in ice I h, ice II, and ice IX were determined using experimental quadrupole co upling constants and a model equation. An averaged bond length of 98.9 pm was obtained for the Ih form, which is approximately 2 pm shorter than that determined by neutron diffraction studies, whereas the bond lengths for the four deuterium sites in ice II and the three sites in ice IX are in fair agreement with experiment. (C) 1993 by John Wiley & Sons, Inc.