Diamond transition to graphite

Phase diagram of carbon. (A) Martensitic transition hex graphite - hex diamond. (B) Fast graphite-to-diamond transition. (C)... 

At 25°C and 1 atm, graphite is the stable form of carbon. Diamond, in principle, should slowly transform to graphite under ordinary conditions. Fortunately for the owners of diamond rings, this transition occurs at zero rate unless the diamond is heated to about 1500°C, at which temperature the conversion occurs rapidly. For understandable reasons, no one has ever become very excited over the commercial possibilities of this process. The more difficult task of converting graphite to diamond has aroused much greater enthusiasm. 

In the case of the graphite-to-diamond transformation, thermodynamic results predict that graphite is the stable allotrope at a fixed temperature at all pressures below the transition pressure and that diamond is the stable aUotrope at all pressures above the transition pressure. But diamond is not converted to graphite at low pressures for kinetic reasons. Similarly, at conditions at which diamond is the thermodynamically stable phase, diamond can be obtained from graphite only in a narrow temperature range just below the transition temperature, and then only with a catalyst or at a pressure sufficiently high that the transition temperature is about 2000 K. 

The enthalpy change for the transition from graphite to diamond is an essential item of information in calculation of the conditions for the geological and industrial production of diamonds. 

Phase Transition of Graphite to Diamond or Diamond-Like Carbon... 

F. Zipoli, M. Bernasconi, and R. Martohak (2004) Constant pressure reactive molecular dynamics simulations of phase transitions under pressure The graphite to diamond conversion revisited. Eur. Phys. J. B 39, p. 41... 

The characteristic of datum (1) shows the shock effects on the starting graphite that resulted in more graphitized structures and diamond formation [25]. The datum (2) shows that the lattice strain in postshock sample II is more severe than that in postshock sample I. The data (3) and (4) suggest that defects play an important role in phase transition of graphite to diamond because the appearance of the diffraction line at 43.88° corresponds to the (111) reflection of diamond. 

Xiao P, Henkelman G (2012) Communication from graphite to diamond reaction pathways of the phase transition. J Chem Phys 137 101101... 

Dong X, Zhou X-F, Qian G-R, Zhao Z, Tian Y, Wang H-T (2013) An ab initio study on the transition paths from graphite to diamond under pressure. J Phys Condens Matter 25 145402... 

KhaliuUin, R., Eshet, H., Kiihne, T, Behler, J., Parrinello, M. Nucleation mechanism for the direct graphite-to-diamond phase transition. Nat. Mater. 10, 693-697 (2011). doi 10.1038/ nmat3078... 

Fig. 6.16 The energetics of the linear transition path from rhombohedral graphite to diamond calculated by DFT, GAP and the Brenner potential...

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