Crystal structures of diamond and lonsdaleite

Models of the crystalline atomic structure of the minerals diamond (cubic) and lonsdaleite (hexagonal). Both are composed of pure carbon in sp3 tetrahedral bonding environment. Diamond is the most stable form (although metastable with respect to graphite at room temperature and pressure) whereas lonsdaleite is only formed at high temperatures and pressures (e.g. in meteorites).

 

Crystal structures taken from the ICSD and then imported into Blender for rendering and exported as STL.

Both structures are oriented so as to make clear the ordering of atoms in the close-packed planes. For the diamond structure, there are sufficient atoms to make at least one conventional cubic unit cell, but it is not easy to find! I have included an image below as a guide (yellow atoms belong to the conventional cell)

 

Boost MeIf you find these models useful for your teaching and education, please boost me. I will be uploading more structures in this series, and happy to receive requests if you have particular one you'd like to see.