Liquid water under vibrational strong coupling: an extended cavity Born-Oppenheimer molecular dynamics study

Abstract: A computational study of liquid water when the system is coupled with a (model) Fabry-Perot cavity is reported. At this end, the Cavity Born-Oppenheimer Molecular Dynamics approach proposed recently (Li et al., Proc. Nat. Acad. Sci. USA, 2020, 117, 18324-18331) is employed and different properties of water under vibrational strong coupling (VSC) are investigated. Different cavity frequencies are considered, corresponding to different modes in the IR spectrum of liquid water: high frequency (corresponding to O-H stretching modes), medium frequency (corresponding to water molecule bending) and low frequencies (corresponding to librational modes). Simulations were done both using classical and quantum nuclear dynamics, this last via Ring Polymer Molecular Dynamics. Similar effects of the cavity are obtained in both cases. Namely, whereas the infrared spectrum is observed to be split for all cavity frequencies, no effects on structural properties are detected. In addition, transport and dynamical properties, including the diffusion coefficient, molecular reorientation and hydrogen bond (HB) jump exchange times, show no effect due to cavity coupling when an extended statistical analysis is performed.