Effects of methanol on crystallization of water in the deeply supercooled region

The interaction of water with adsorbed methanol and butane is investigated and the crystallization mechanism of deeply supercooled water is discussed. Amorphous solid water becomes viscous liquid at temperatures greater than 136 K, and then a more fluidized liquid phase appears at 165 K, thereby engendering film dewetting. Crystallization occurs only in the dewetted films as revealed from the abrupt redshift and narrowing of the infrared absorption band. If methanol is incorporated in the bulk of water, crystallization occurs at lower temperatures (152 K) because water is nucleated by methanol. The crystallization in the viscous liquid phase (136 K < T < 165 K) is thought to be quenched without such nuclei, whereas spontaneous nucleation occurs in supercooled liquid water that appears at 165 K. The butane molecules, which are hydrated in the bulk of amorphous solid water, are released almost completely up to 165 K, although this dehydration channel is suppressed considerably if crystallization is induced by methanol. It is therefore suggested that butane dehydration is related to the phase transition of liquidlike water rather than crystallization.