A few years ago, I was fascinated by the news of the discovery of a new Carbon allotrope based on first-principle simulations by using USPEX software described here. Or particularly this article:
Zhu Q., Oganov A.R., Salvado M., Pertierra P., Lyakhov A.O. (2011). Denser than diamond:ab initio search for superdense carbon allotropes. Phys. Rev. B83, 193410, download here.