PNNL

Abstract

The molecular reorientation associated with the dynamics of the hydrogen-bond network in liquid water is investigated using quantum molecular dynamics simulations performed with the ab-initio based TTM3-F interaction potential. The reorientation dynamics calculated at different temperatures are found to be in excellent agreement with the corresponding experimental results obtained from polarization-resolved, femtosecond mid-infrared, pump-probe spectroscopic measurements. A comparison with analogous results obtained from classical molecular dynamics simulations with the same interaction potential clearly indicates that the explicit inclusion of nuclear quantum effects is critical for reproducing the measured time-dependence of the anisotropic signal. The analysis of the isotope effects indicates that the quantum effects involved in the water reorientation are mainly associated with zero-point energy differences although tunneling contributions may also be at play near the melting point.