Diamondization of Bulk and Slabs of Graphite

Abstract

Graphite and diamond are allotropes of carbon with comparable energies. However, the formation of diamond from graphite requires the application of high pressures (physical method), typically above 10 GPa, as is currently done using the HPHT method (High Pressure, High Temperature). From the chemical point of view, the application of pressure forces a change of hybridization of sp2 carbon atoms, as in graphite, to sp3, as in diamond. The mechanism of this phase change, however, is not trivial, as there are two forms of graphite that coexist, rhombohedral graphite (RG) and hexagonal graphite (HG), and the same occurs with the diamond; there is the cubic diamond (CD) and the hexagonal (HD). Here the RG→CD and HG→HD processes are studied. Besides the physical method to force the change of hybridization, one can think on a chemical method that leads to the same result. A change in hybridization of carbon atoms can happen with the adsorption of hydrogen or fluorine atoms on different graphitic systems with more than one layer...