BC8 superdiamonds are harder than any known material, but they likely only exist in the cores of giant exoplanets. Now, the Frontier supercomputer has unraveled the secret of their formation, a finding that could lead to their production on Earth.
Diamonds not only make eye-catching jewelry, but they're used in a variety of applications around the world. As the world's hardest substance – and thanks to their unique makeup – they have a role in everything from drilling advanced geothermal wells to serving as semiconductors in nuclear batteries.
So imagine what possibilities might open up if we could create a substance that's even harder than the hardest material known to humanity.
Actually, that's what scientists have envisioned for years. They have predicted that a material which has eight carbon atoms packed into it for every four of those found in a diamond, probably exists under the extreme heat and pressure found in the cores of planets at least two times bigger than Earth.
Creating this "superdiamond" known as BC8 (for eight-atom body-centered cubic) might be possible in the lab, but the conditions that need to be replicated are challenging to say the least. A replicator would need to reach 10 million times the pressure of the Earth's atmosphere and temperatures approaching that of the sun's surface, so running multiple physical experiments to attempt the production of BC8 are a little impractical.
Enter the world's fastest supercomputer: Frontier at the Department of Energy's Oak Ridge Lab. It has the power to run millions of atomic modeling situations over millions of sets of conditions to determine exactly what it would take to form BC8. A team of researchers led by Ivan Oleynik, the study’s lead author and a professor of physics at the University of South Florida, got permission to access Frontier to see if it could help them crack the BC8 code – and it worked.
Philosopher's stone
"It’s the ultimate challenge of high-pressure physics," said Oleynik. "It’s our version of the philosopher’s stone that medieval alchemists believed would turn lead into gold if only they could find it. The alchemists didn’t have Frontier."
The professor and his team fed Frontier an astounding amount of data to train a software module known as LAMMPS, which stands for Large-scale Atomic/Molecular Massively Parallel Simulator software module, to carry out the necessary computations. Oleynik said other computers simply bogged down too much to run the program.
"We basically fingerprinted every atomic environment around each atom in a billion-atom system that could result during the system’s evolution at extreme pressures and temperatures," Oleynik said. "Without Frontier, this would have been impossible."
"For this study, we needed to simulate more than a billion atoms while performing up to a million time steps in molecular dynamics simulations," he added. "We had access to other supercomputers, but none of them even had enough computational power to handle that many atoms."
'Shocking' discovery
After running LAMMPS for about 24 hours using 8,000 of Frontier's more than 9,400 nodes, the team got an answer that showed a unique and slightly surprising step that would be necessary for turning carbon into BC8. They found that traditional diamonds would first need to melt before the carbon liquid could then rearrange itself into BC8's super-strong structure.
"It’s a new discovery in that sense because in most cases materials transform from one crystalline phase into another by concerted rearrangement of an atomic structure," Oleynik said. "But the carbon bonds that make up a diamond are so strong, we have to melt the diamond in order to transform it into a new BC8 crystalline phase. So that adds another layer to this process with even more extreme pressures and temperatures – 12 million times the pressure of Earth’s atmosphere and 5,000 K, which is close to the temperature of the sun’s surface."
The research revealed that such conditions could be created via a series of shockwaves, and provided the team with exactly the right level of such waves to reach the temperature and pressure readings necessary to form BC8.
Now the team is beginning to test out that knowledge by attempting to synthesize BC8 at Lawrence Livermore National Laboratory's National Ignition Facility, a stadium-sized nuclear fusion facility that uses 192 powerful lasers to create temperatures in excess of 180 million degrees Fahrenheit and pressures of more than 100 billion Earth atmospheres.
"Thanks to Frontier, we have a good chance of success," concluded Oleynik. "It’s still an extreme challenge with no guarantees, but we have great confidence in these results."
The following video provides more information about the findings.
The results of the study have been reported in The Journal of Physical Chemistry Letters.
Source: Oak Ridge National Laboratory