On the cover of the Journal of Physical Chemistry A is the article reporting polymorphism in bromine clathrate hydrates, discovered by the Janda and Apkarian groups, through micro-Raman spectroscopy on single crystals. One of the first discovered clathrates, Br2-clathrate hydrates have played a central role in our understanding of the stability of clathrates, and more generally, of solid solutions. The stacking of the Archimedean polyhydra of water, through hydrogen bonds, allows for a very large number of ways to tile 3-D space. Yet, not all possible structures are realized. Identifying the units that acquire special stability has been a challenge, which is in good part resolved by the report.
Sunday, February 10, 2008