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arXiv · 2401.08884

Extreme Metastability of Diamond and its Transformation to BC8 Post-Diamond Phase of Carbon

Kien Nguyen-Cong·Jonathan T. Willman·Joseph M. Gonzalez·Ashley S. Williams·Anatoly B. Belonoshko·Stan G. Moore·Aidan P. Thompson·Mitchell A. Wood·Jon H. Eggert·Marius Millot·Luis A. Zepeda-Ruiz·Ivan I. Oleynik
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Abstract

Diamond possesses exceptional physical properties due to its remarkably strong carbon-carbon bonding, leading to significant resilience to structural transformations at very high pressures and temperatures. Despite several experimental attempts, synthesis and recovery of the theoretically predicted post-diamond BC8 phase remains elusive. Through quantum accurate, multi-million atom molecular dynamics (MD) simulations, we have uncovered the extreme metastability of diamond at very high pressures, significantly exceeding its range of thermodynamic stability. We predict the post-diamond BC8 phase to be experimentally accessible only within a narrow high pressure-temperature region of the carbon phase diagram. The diamond to BC8 transformation proceeds through pre-melting followed by BC8 nucleation and growth in the metastable carbon liquid. We propose a double-shock compression pathway to achieve BC8 synthesis, which is currently being explored in theory-inspired experiments at the National Ignition Facility.

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Kien Nguyen-Cong, Jonathan T. Willman, Joseph M. Gonzalez, Ashley S. Williams, Anatoly B. Belonoshko, Stan G. Moore, Aidan P. Thompson, Mitchell A. Wood, Jon H. Eggert, Marius Millot, Luis A. Zepeda-Ruiz, Ivan I. Oleynik. 2024-01-16. Extreme Metastability of Diamond and its Transformation to BC8 Post-Diamond Phase of Carbon. https://arxiv.org/abs/2401.08884

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