Ice, but in a better state of order – Ice II

What does it looks like?

The beautiful, web-like, structure of ice II. Image generated by the VESTA (Visualisation for Electronic and STructural Analysis) software http://jp-minerals.org/vesta/en/

What is it?

By a strange coincidence, all of the water-ice structures we've featured so far this year have been disordered. It's a feature of many of the crystal structures of ice that the water molecules do not sit idle, and in fact flip about the central oxygen atom. So in many forms of ice, from the type found in our freezers and ice caps, to the types found on other planets the hydrogen atoms are never still and are constantly jumping about.

But Ice II is an exception to this, and was the first 'proton ordered' ice discovered (by proton ordered, we're referring to the fact that the hydrogen atoms are not jumping about any more!). To create this ice structure requires cold temperatures and a little bit of pressure, but this is enough to 'freeze' the water molecules into position.

Where did the structure come from?

Though Ice II was discovered by Percy Bridgman, its crystal structure was found by Kamb in 1964 using X-ray and neutron diffraction. The structure of Ice II is #9015045 in the Crystallography Open Database.

Tags: high pressure   historic   ice   neutron diffraction