Understanding the mechanism of shockwave induced graphite-to-diamond phase transition

Nanodiamonds (NDs) manufactured from graphite exhibit superior physical properties that are desired in enormous applications, but the graphite-to-diamond phase transition mechanism in nonequilibrium synthesis is poorly understood, hindering the optimization and control of the manufacturing process. Herein, in this paper, molecular dynamics and density function theory simulations were conducted to unravel the graphite-to-diamond phase transition mechanism in the shockwave-based ND manufacturing process. Our simulations first reveal the synergistic effect of incident and reflected shockwaves, which stabilizes the positions of carbon atoms, leading to the formation of the interlayer carbon bonds and diamond phase. Moreover, simulation results exhibit the tiered movement of the graphite layers and the frequent exchange of kinetic energy between the adjacent graphite layers, indicating the propagation of the incident shockwaves and the initiation of the reflected shockwaves. Finally, the simulations shed light on the origin of the byproduct such as amorphous carbon and carbon liquid during the shockwave-based ND manufacturing. This work advances the fundamental understanding of the graphite-to-diamond phase transition mechanism and will promote the design and optimization of related manufacturing processes.