Spatiotemporal heterogeneity and energy landscape in liquid water

Correlation between the spatial heterogeneity and the collective motions of molecules is studied with molecular dynamics simulation of liquid water. Analyses based on the order parameter of structural fluctuations show that liquid water is a composite of high-density amorphous (HDA)-like regions and low-density amorphous (LDA)-like regions. Structural relaxation modes are localized in the HDA-like regions, so that the anomalous kinetic slowing down in the supercooled regime should be correlated to the HDA–LDA transformation. A simple random energy model is discussed to show the relation between the possible liquid–liquid transition and the glass transition.