heterogeneous nucleation

When ice nuclei are present, heterogeneous ice nucleation can occur at warmer temperatures.

Nucleation processes are classed as heterogeneous or homogeneous. In the former, the surface of some different substance, such as a dust particle or the wall of the container, acts as the centre upon which the first atoms, ions, or molecules of the crystal become properly oriented; in the latter, a…

The temperature of heterogeneous nucleation (nucleation beginning at the surface of foreign particles) depends on the nature of the particles, but it is generally several degrees below the freezing point. Again, supercooling of this magnitude is not observed in most naturally occurring waters, although some researchers argue that…

…float in the air (heterogeneous nucleation). The nuclei consist predominantly of silicate minerals of terrestrial origin, mainly clay minerals and micas. At still lower temperatures, ice may form directly from water vapour (homogeneous nucleation). The influence of the atmospheric water vapour depends mainly on its degree of supersaturation with respect…