High-purity cubic phase offers new insight into ice physics

For the first time, researchers have synthesised large quantities of a rare form of ice with a cubic crystal packing structure.

There are at least 18 known forms of water ice – but only two of these occur naturally on Earth. Under atmospheric pressure, liquid water usually freezes to make ice Ih – a highly stable form with a hexagonal crystal structure. Another much less common form of ice, which might form naturally in the upper atmosphere, is called ‘cubic ice’ because of the three-dimensional symmetry seen in its crystal structure.