Minimum number of water molecules to create an ice cube

Work reported in the journal Science (2012, 337, 1529) recently has shown that the minimum number of water molecules required to give the crystal structure of ice is 275. With fewer water molecules water clusters have liquid-like IR spectra. As the cluster grows beyond the magic number of 275 crystallization to give a nanocrystal occurs and is complete by the time a cluster reaches some 475 water molecules. The researchers (teams led by Thomas Zeuch from Göttingen and Udo Buck from the Max Planck Institute) stabilisied various water clusters by surrounding them with a sheath of sodium cations.