Atomistic Computational Analysis of the Loading Orientation-Dependent Phase Transformation in Graphite under Compression

In this work, we perform atomistic simulations to study the phase transformations (PT) in graphite under compression. Our major findings are: (1) when the compression is parallel to the basal plane, graphite layers buckle, kink bands form, and then the diamond nucleates at the intersection of kink bands; the initially introduced dislocations block the graphite layer slippage and promote the graphite-to-diamond PT; (2) instead, when the sample is compressed normal to the basal plane, no buckling is observed, and in this situation, the pre-existing dislocations delay the structure change; and (3) the PT is found to be controlled by local stresses from which a criterion can be formulated for detecting the graphite lattice instability. Despite the limited length scales in our atomistic models, the above results may support the search for new routes to fabricate artificial diamonds at a significantly less cost than that required by traditional techniques.