Isotope quantum effects in the electron momentum density of water.

The isotope quantum effects in the ground-state electron momentum density of water are studied at temperatures ranging from 5 to 90 °C by combining Compton scattering experiments utilizing synchrotron radiation and computational analysis within density functional theory. We observe clear differences in the momentum density between normal and heavy water at room temperature, which are interpreted as predominantly reflecting intramolecular structural differences. The changes in the momentum density upon increasing the temperature are found to be larger for heavy than for normal water, which is attributed primarily to temperature-induced intramolecular structural effects. Both model computations and an ab initio approach qualitatively reproduce the changes in the momentum density as a function of temperature. [ABSTRACT FROM AUTHOR]