page_title: Supercooling
section_title: Constitutional supercooling
hierarchical_section_title: Supercooling / Constitutional supercooling
caption_attribution_description: English: constitutional supercooling - phase diagram, concentration, and temperature
context_page_description: Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid or a gas below its freezing point without it becoming a solid. It achieves this in the absence of a seed crystal or nucleus around which a crystal structure can form. The supercooling of water can be achieved without any special techniques other than chemical demineralization, down to −48.3 °C. Droplets of supercooled water often exist in stratus and cumulus clouds. An aircraft flying through such a cloud sees an abrupt crystallization of these droplets, which can result in the formation of ice on the aircraft's wings or blockage of its instruments and probes.
  Animals utilize supercooling to survive in extreme temperatures, as a last resort only. There are many techniques that aid in maintaining a liquid state, such as the production of antifreeze proteins, which bind to ice crystals to prevent water molecules from binding and spreading the growth of ice. The winter flounder is one such fish that utilizes these proteins to survive in its frigid environment.
context_section_description: Constitutional supercooling, which occurs during solidification, is due to compositional solid changes, and results in cooling a liquid below the freezing point ahead of the solid–liquid interface.  When solidifying a liquid, the interface is often unstable, and the velocity of the solid–liquid interface must be small in order to avoid constitutional supercooling.
  Supercooled zones are observed when the liquidus temperature gradient at the interface is larger than the temperature gradient.
  or
  The slope of the liquidus phase boundary on the phase diagram is 
  The concentration gradient is related to points,  and , on the phase diagram:
  For steady-state growth  and the partition function  can be assumed to be constant. Therefore, the minimum thermal gradient necessary to create a stable solid front is as expressed below.
  For more information, see the equation (3) of
caption: Constitutional supercooling – phase diagram, concentration, and temperature
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