Over the last 30 years, coal-fired electricity generation in the U.S. more than halved as a share of all generation, falling to a nearly half-century low. But is there a role for coal in a post-fossil fuel world? Researchers from Ohio University leveraged supercomputing at the Pittsburgh Supercomputing Center (PSC) to study how coal can be converted into useful, emissions-free materials.
The researchers sought to study the conversion of coal – which has a three-dimensional structure – into graphite, which can be used for everything from pencils to electric car batteries (which require many pounds of graphite).
“The way this [work] came about is there are some engineers here … doing some great work [on carbon-neutral] things with coal,” said David Drabold, a professor of physics at Ohio University, in an interview with PSC’s Ken Chicchia. “You don’t want to burn it for obvious reasons; but can you make construction materials out of it, high-value materials out of it, like graphite? [We’re] really interested in the question: can we get graphite out of the stuff?”
The researchers simulated a proxy for coal consisting of carbon atoms randomly arranged, then subjected that simulated coal proxy to extreme pressure and temperature. They ran these simulations – which, at first were based on density functional theory, then on Gaussian approximation potential – on PSC’s Bridges-2 system, which leverages AMD, Intel and Nvidia hardware. The simulations did result in graphite sheets, but with some amorphous deformations: pure graphite consists entirely of six-carbon rings, while some of the simulated rings had five- or seven-carbon structures.
“To push out the amorphous-graphite paper we needed to do a lot of serious analysis,” explained Chinonso Ugwumadu, a PhD student in physics at Ohio University who led the initial computational work alongside fellow graduate student Rajendra Thapa. “Compared to other systems which we have, Bridges is the fastest and most accurate. Our home systems … take about two weeks to simulate 160 atoms. With Bridges, we can run 400 atoms over six to seven days using density functional theory.”
Subsequent simulations studying carbon structures in a different form instead created graphite sheets that curved inward – so not sheets at all, but rather carbon nanotubes, which themselves have a wide range of uses, from stealth technology to biosensors. The researchers also suggested that designers could exploit the irregularities that appeared in both the graphite sheets and the nanotubes, building the amorphousness into the function of an application.
The researchers published two papers based on their most recent findings and are continuing their research in this area.
To learn more about this research, read the reporting from PSC’s Ken Chiacchia here.