Wang, J. T., C. F. Chen, et al. (2010). "Phase stability of carbon clathrates at high pressure." Journal of Applied Physics 107(6): 063507.

Group-IV element clathrates have attracted considerable interest in recent years. Here, we report an ab initio study on the structural stability of carbon clathrates at high pressure and identify fcc-C(136) clathrate as the third most stable carbon phase after cubic diamond and hexagonal graphite. A pressure-induced phase transition is predicted to occur around 17 GPa from hexagonal graphite to fcc-C(136), which is more stable than other carbon clathrates such as hex-C(40) and sc-C(46), and the recently predicted metastable M-carbon up to 26 GPa. Phonon dispersion calculations confirm the dynamic stability of fcc-C(136) as well as diamond.