Vibrational spectroscopies in liquid water: on temperature and coordination effects in Raman and infrared spectroscopies

TL;DR

This study uses molecular dynamics simulations to analyze how temperature, hydrogen bonding, and electronic structure methods influence the vibrational spectra of liquid water, providing detailed insights into its complex physics.

Contribution

It offers a comprehensive analysis of vibrational spectra in water, highlighting the effects of temperature, hydrogen bonding coordination, and electronic structure methods with quantitative insights.

Findings

Vibrational frequencies vary with temperature and hydrogen bonding coordination.

Different electronic structure methods impact force calculations and spectral results.

Isotopic mixtures and dielectric constants are characterized in water.

Abstract

Water is an ubiquitous liquid that has several exotic and anomalous properties. Despite its apparent simple chemical formula, its capability of forming a dynamic network of hydrogen bonds leads to a rich variety of physics. Here we study the vibrations of water using molecular dynamics simulations, mainly concentrating on the Raman and infrared spectroscopic signatures. We investigate the consequences of the temperature on the vibrational frequencies, and we enter the details of the hydrogen bonding coordination by using restrained simulations in order to gain quantitative insight on the dependence of the frequencies on the neighbouring molecules. Further we consider the differences due to the different methods of solving the electronic structure to evaluate the forces on the ions, and report results on the angular correlations, isotopic mixtures HOD in H$_2$O/D$_2$O and and the dielectric constants in water.