Dynamics of vibrational spectral diffusion in water: Effects of dispersion interactions, temperature, density, system size and fictitious orbital mass

Abstract

We have carried out a series of ab initio molecular dynamics simulations to investigate the effects of dispersion interactions, temperature, density, system size and fictitious orbital mass on the dynamics of vibrational spectral diffusion and other dynamical properties of liquid water. While most of the simulations are performed at room temperature, the effects of temperature are looked at by carrying out additional simulations at 25 K above the reported melting point of ab initio water for our chosen density functionals. Apart from the dynamical properties, we have also looked at some of the equilibrium properties such as structure, frequency distributions and frequency-structure correlations for all the systems. In general, it is found that the inclusion of dispersion interactions makes the dynamics faster. The effects of system size, orbital mass and temperature are also discussed for the systems considered here.