Nuclear Quantum Effects on the Vibrational Dynamics of Liquid Water

TL;DR

This study uses quantum-mechanical simulations to show that nuclear quantum effects significantly influence the vibrational and hydrogen bond dynamics in liquid water, causing frequency shifts and faster vibrational relaxation.

Contribution

It provides the first detailed analysis of nuclear quantum effects on vibrational dynamics in liquid water using path-integral molecular dynamics simulations.

Findings

Nuclear quantum effects cause a ~130 cm$^{-1}$ redshift in vibrational frequencies.

Quantum effects accelerate vibrational dynamics by up to 30%.

Faster decay of correlation functions aligns with recent experimental observations.

Abstract

Based on quantum-mechanical path-integral molecular dynamics simulations the impact of nuclear quantum effects on the vibrational and hydrogen bond dynamics in liquid water is investigated. The instantaneous fluctuations in the frequencies of the O-H stretch modes are calculated using the wavelet method of time series analysis, while the time scales of the vibrational spectral diffusion are determined from frequency-time correlation functions, joint probability distributions, as well as the slope of three-pulse photon echo. We find that the inclusion of nuclear quantum effects leads not only to a redshift of the vibrational frequency distribution by around 130~cm$^{-1}$, but also to an acceleration of the vibrational dynamics by as much as 30$\%$. In addition, quantum fluctuations also entail a significantly faster decay of correlation in the initial diffusive regime, which is agreement with recent vibrational echo experiments.