Chemical modifications of C-60 under the influence of pressure and temperature: From cubic C-60 to diamond

Solid C-60 undergoes a series of irreversible transformations as a function of temperature and pressure. It starts with a polymerization through a 2+2 cycloaddition mechanism. Then, as pressure and temperature increase, it transforms into diamond through a succession of states composed, in particular, by a very hard shiny black amorphous material and an amorphous carbon containing compressed graphite. At room temperature and high pressure (20 GPa) together with high shear stresses, a transparent amorphous material at least as hard as diamond is formed.