Dynamics of low-temperature water are driven by electrostatics

Abstract

Non-Gaussian dynamics in low-temperature liquids are assigned to spatial fluctuations of relaxation times and linear transport coefficients (dynamic heterogeneity). In contrast, molecular dynamics simulations of SPC/E water assign non-Gaussian dynamics to electrostatic intermolecular interactions growing in prominence with lowering temperature. Translational non-Gaussian parameters and rotational/translational relaxation times follow master curves produced by either changing temperature or the liquid’s dipole moment. Static and dynamic compensation relations found for bulk water are assigned to the separation of time scales between density and electrostatic fluctuations.