Speaker
Description
Although the influence of nuclear quantum effects (NQE) in the properties of liquid water is well-known, the magnitude of their effects depends strongly on the specific conditions and property considered. It has been suggested that this could be due to competing quantum effects, where proton delocalization in the direction of the H-bond would reinforce it, while delocalization in other directions would distort and therefore weaken the H-bonds [1]. While the effect of NQEs in the structure of liquid water remains controversial, both from the experimental and computational approaches, they are much stronger in the rotational and translational dynamics and the subject of intense theoretical and computational efforts [1,2]. We have used polarized QENS in LET to explore the extent of NQEs in light (H$_2$O) and heavy (D$_2$O) water at 278 K and compared the experimental spectra with classical simulations in order to separate the effect of NQEs from the classical isotopic mass effect. The self-dynamics of protons in H$_2$O and D$_2$O as obtained from the analysis of the incoherent dynamical cross section will be presented, together with an analysis of the possibilities and limitations of using this information to improve the classical potentials.
[1] M. Ceriotti et al: “Nuclear Quantum Effects in Water and Aqueous Systems: Experiment, Theory, and Current Challenges”, Chem. Rev. 2016, 116, 7529−7550.
[2] N. Stolte et al: “Nuclear Quantum Effects in Liquid Water Are Marginal for Its Average Structure but Significant for Dynamics”, J. Phys. Chem. Lett. 2024, 15, 12144−12150.
