ABSTRACT
The diagram above shows the 12 carbon atoms of hexamethylbenzene (HMB) positioned within the unit cell. The carbon atoms all lie in a plane. The hydrogen atoms are omitted. Calculating detailed structural relationships such as the distances and the angles between the atoms of a crystal is an essential part of crystallography. The analysis of HMB by Kathleen Lonsdale was the first definitive proof of the planarity of the benzene ring.
