A first principles simulation study of fluctuations of hydrogen bonds and vibrational frequencies of water at liquid-vapor interface

We present a theoretical study of the structure and dynamics of water-vapor interface by means of ab initio molecular dynamics simulations. The inhomogeneous density, hydrogen bond and orientational profiles, voids and vibrational frequency distributions are investigated. We have also studied various dynamical properties of the interface such as diffusion, orientational relaxation, hydrogen bond dynamics and vibrational frequency fluctuations. The diffusion and orientational relaxation of water molecules are found to be faster at the interface which can be correlated with the voids present in the system. The hydrogen bond dynamics, however, is found to be slightly slower at the interface than that in bulk water. The correlations of hydrogen bond relaxation with the dynamics of vibrational frequency fluctuations are also discussed.

The structure and dynamics of water-vapor interface are investigated by means of ab initio molecular dynamics simulations. The primary goal is to study the fluctuations of hydrogen bonds and their relations to vibrational spectral diffusion of interacial molecules.Highlights► Water-vapor interfacial properties are investigated by ab initio molecular dynamics. ► Increase of voids lead to faster diffusion and orientational relaxation of interfacial water. ► Hydrogen bond dynamics is slightly slower at the interface due to lack of cooperative effects. ► The correlations of hydrogen bond relaxation with vibrational frequency fluctuations are discussed.