A smashing crystal structure – Nickel sulfide

What does it look like?

Image generated by the VESTA (Visualisation for Electronic and STructural analysis) software http://jp-minerals.org/vesta/en/

What is it?

It's rare, but sometimes a glass window can spontaneously smash. Though not too dangerous, this can be a little shocking, especially if you’re in a high-rise building!

The crystals structure we're featuring today is thought to be one of the reasons behind why this happens. Glass can often have small impurities of nickel sulfide, and this material can actually exist as two crystal forms – an alpha phase (which is hexagonal) and a beta phase (which is rhombohedral and the structure we've pictured above). It's thought that temperature can cause this impurity to change between these two structures, and when this happens there's a small volume change of the material. This small volume change puts extra stress on the window glass and can cause it to smash!

Where does the structure come from?
Beta NiS, the rhombohedral form, is #9004078 in the Crystallography Open Database.

Tags: glass   sulfide