Identification of two distinct structural and dynamical domains in an amorphous water cluster

This investigation is focused on dynamics and structure of an amorphous water cluster (H2O)116. The cluster was obtained in a previous study by simulation of the condensation of amorphous ice. The time evolution of the cluster is studied on a ∼400 ps time scale, using the classical trajectory technique at different temperatures. Two distinct structural and dynamical domains are identified. At 36 K the cluster displays glass-like behavior. There is also a broad distribution of molecular states extending from 1- to 5-coordinated water molecules. Upon heating to 100 K the cluster undergoes a transition to a more compact structure. The molecular energy distribution narrows down and is dominated by 3- and 4-coordinated molecules. After the transition the cluster displays liquid-like characteristics. All these changes are not reflected by the normal frequency distribution of structures along the trajectory.