March 20, 2024 — While diamond has long been hailed as the epitome of strength among materials, scientists have long speculated the existence of a carbon phase even tougher than diamond. Now, researchers are inching closer to creating this elusive material right here on Earth.
The carbon phase in question is the eight-atom body-centered cubic (BC8) crystal—a unique form distinct from diamond yet bearing striking similarities. Predicted to exhibit a staggering 30% greater resistance to compression than diamond, BC8 is theorized to exist at the core of carbon-rich exoplanets. If successfully synthesized under ambient conditions, BC8 could revolutionize material science, earning the moniker of a ‘super-diamond.’
“The BC8 phase of carbon at ambient conditions would be a new super-hard material that would likely be tougher than diamond,” explains Ivan Oleynik, a physics professor at the University of South Florida (USF) and senior author of a recent paper published in The Journal of Physical Chemistry Letters.
Despite numerous attempts to synthesize BC8, including previous endeavors at the National Ignition Facility (NIF), the elusive carbon phase has remained beyond reach. However, scientists like Marius Millot from Lawrence Livermore National Laboratory (LLNL) remain optimistic, speculating its potential presence in carbon-rich exoplanets.
Recent astrophysical observations hint at the existence of such planets, where extreme pressures exceeding millions of atmospheres in their deep interiors could foster the formation of exotic carbon structures like diamond and BC8.
With BC8 also being a recoverable high-pressure phase of silicon and germanium, the team is hopeful about its stability under ambient conditions. According to LLNL scientist Jon Eggert, BC8’s perfect tetrahedral structure, akin to diamond but without its cleavage planes, holds promise for unparalleled toughness.
Leveraging the capabilities of Frontier, the world’s fastest exascale supercomputer, the team conducted multi-million atomic molecular dynamics simulations. These simulations unveiled the extreme metastability of diamond under very high pressures, paving the way for understanding BC8 synthesis pathways.
The study’s significance lies in shedding light on the challenges hindering previous synthesis attempts while offering viable compression pathways to access the elusive BC8 phase. The team remains committed to realizing this breakthrough, with ongoing collaborations and experiments aimed at materializing BC8 synthesis.
With aspirations to one day grow BC8 super-diamond in the laboratory, scientists like Kien Nguyen Cong, the paper’s first author, now a postdoctoral researcher at LLNL, and their collaborators, are pioneering the path towards unlocking the secrets of this extraordinary carbon phase.
