Surface freezing

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Surface Freezing is long range crystalline ordering at the surface of a liquid. It usually occurs in alkanes and long chained hydrocarbons. In most cases the hydrocarbons orient normal to the plane of the surface, and pack in the hexagonally close packed structure. Also, it has only been observed in alkanes that have a degree of polymerization between 14 and 50. It is the opposite of the more common effect known as surface melting. Although it was discovered by John Earnshaw at Queens University in the early 1990s, it is still not well understood.


It is not well understood what causes surface freezing. It seems there should be massive entropic penalties for having it. One theory that tries to avoid these entropic penalties states that the hydrocarbon chains, when normal to the surface, can experience fluctuations along their long axis. These fluctuations are enough to prevent the rotation of the chains down into the bulk liquid. Furthermore, the molecules are tightly packed, again preventing the rotation.


There were no applications that I could find for surface freezing.


A. V. Tokachenko and Y. Rabin, Phys. Rev. E 55, 778 (1997).