desublimates

Desublimation, or deposition, is the phase transition in which a substance changes directly from a gas to a solid, bypassing the liquid phase. It is the reverse of sublimation. Desublimation occurs when a vapor is cooled or its pressure is reduced such that the solid phase becomes more stable than the liquid or gaseous forms. In many substances this happens at temperatures at or below the triple-point temperature, or on surfaces where rapid cooling promotes direct solidification. A common everyday example is the formation of frost from water vapor on cold surfaces.

The solid material formed by desublimation is called a desublimate; in general, desublates or desublimates can refer to the solids produced in a desublimation process. Desublimation is important in both natural settings and industrial contexts. In nature, frost, ice deposition on windows, and other surface crystallization result from deposition of vapors at low temperatures. In technology, desublimation can occur in vacuum and low-temperature environments where vapors condense directly as crystalline films on cooler substrates, contributing to certain physical vapor deposition and crystal-growth processes.

Desublimation is distinguished from condensation (gas to liquid) and from sublimation (solid to gas). It is also related to the study of phase diagrams and surface interactions, where temperature, pressure, and substrate characteristics determine whether deposition or alternative phase transitions occur.