posted on 2024-01-25, 09:05authored byKien 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
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 multimillion 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
premelting followed by BC8 nucleation and growth in the metastable
carbon liquid. We propose a double-shock compression pathway for BC8
synthesis, which is currently being explored in experiments at the
National Ignition Facility.