Nanoclusters and Amorphous Ice Flakes Built from Water Dimers

Abstract The water-solid interaction is fundamentally important for understanding and controlling the structures of interfacial water. Here we study the initial stage of water adsorption and nucleation on a Cd(0001) surface, through a combination of low temperature scanning tunnelling microscopy (STM) experiments and first-principles density-functional theory (DFT) calculation. Water is found to aggregate into various clusters with the dominant of water dimers. Particularly, the amorphous ice nanoflakes are built exclusively from water dimers. Driven by the electric field from a STM tip, the water dimers can hop across the surface, detach from a cluster with subsequent attaching to another, or rotate or diffuse within the amorphous ice nanoflakes. DFT calculations demonstrate that the ultrahigh stability of water dimers results from the adsorption-induced enhancement of dipole moment of water.