A Revisited Mechanism of the Graphite-to-Diamond Transition at High Temperature

SC Zhu and XZ Yan and J Liu and AR Oganov and Q Zhu, MATTER, 3, 864-878 (2020).

DOI: 10.1016/j.matt.2020.05.013

The graphite-diamond transition, under high-pressure and high- temperature conditions, has been a central subject in physical science. However, its atomistic mechanism remains under debate. Employing large- scale molecular dynamics (MD) simulations, we report a mechanism whereby the diamond nuclei in the graphite matrix propagate in two preferred directions, among which the graphite 120 is about 2.5 times faster than 001. Consequently, cubic diamond (CD) is the kinetically favorable product, while only a few hexagonal diamonds (HDs) can exist as the twins of CDs. The coherent interface of t-(100)gr//(11-1)cd + 010gr//1-10cd observed in MD simulation was confirmed by our high- resolution transmission electron microscopy experiment. The proposed mechanism not only clarifies the role of HD in graphite-diamond transition but also yields atomistic insight into strengthening synthetic diamond via microstructure engineering.

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