Nuclear Quantum Effects in Water Reorientation and Hydrogen-Bond Dynamics

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Chemical Physics

Background:

• Understanding molecular dynamics is crucial for chemical processes.
• Nuclear quantum effects (NQEs) can influence molecular behavior.
• Water's hydrogen-bond dynamics are fundamental to its properties.

Purpose of the Study:

• To provide a molecular description of nuclear quantum effects on water reorientation.
• To investigate the impact of NQEs on hydrogen-bond dynamics in H2O and D2O.
• To elucidate the mechanisms behind NQEs' influence on water dynamics.

Main Methods:

• Combined classical and ring polymer molecular dynamics simulations.
• Employed the molecular jump model for analysis.
• Investigated liquid H2O and D2O.

Main Results:

• NQEs accelerate H2O dynamics by approximately 13% compared to classical simulations.
• NQEs have a negligible net effect on D2O dynamics.
• Large angular jumps are the dominant reorientation pathway, with NQEs increasing the jump rate.
• NQEs do not alter jump amplitude distributions or show significant tunneling.
• Faster jump dynamics correlate with decreased OO radial distribution function structuring.
• This is attributed to the competition between librational and OH stretch zero-point energies on hydrogen-bond strength.

Conclusions:

• Nuclear quantum effects significantly impact water reorientation dynamics in H2O.
• The primary mechanism is an increased rate of hydrogen-bond partner exchange.
• Quantum effects on water's hydrogen-bond dynamics are isotope-dependent.