- Number 419 |
- August 4, 2014
Supercomputers reveal strange, stress-induced transformations in world's thinnest materials
Top and side views of soft mode instabilities
in strained monolayer materials. In
graphene, boron nitride, and graphane the
backbone distorts towards isolated six-atom
rings, while molybdenum disulfide
undergoes a distinct distortion towards
trigonal pyramidal coordination.
Interested in an ultra-fast, unbreakable, and flexible smart phone that recharges in a matter of seconds? Monolayer materials may make it possible. These atom-thin sheets—including the famed super material graphene—feature exceptional and untapped mechanical and electronic properties. But to fully exploit these atomically tailored wonder materials, scientists must pry free the secrets of how and why they bend and break under stress.
Fortunately, researchers have now pinpointed the breaking mechanism of several monolayer materials hundreds of times stronger than steel with exotic properties that could revolutionize everything from armor to electronics. A Columbia University team used supercomputers at Brookhaven Lab to simulate and probe quantum mechanical processes that would be extremely difficult to explore experimentally.
They discovered that straining the materials induced a novel phase transition—a restructuring in their near-perfect crystalline structures that leads to instability and failure. Surprisingly, the phenomenon persisted across several different materials with disparate electronic properties, suggesting that monolayers may have intrinsic instabilities to be either overcome or exploited. The results were published in the journal Physical Review B.
“Our calculations exposed these monolayer materials’ fundamental shifts in structure and character when stressed,” said study coauthor and Columbia University Ph.D. candidate Eric Isaacs. “To see the beautiful patterns exhibited by these materials at their breaking points for the first time was enormously exciting—and important for future applications.”
The team virtually examined this exotic phase transition in graphene, boron nitride, molybdenum disulfide, and graphane—all promising monolayer materials. Isaacs and his collaborators used a mathematical framework called density functional theory (DFT) to describe the quantum mechanical processes unfolding in the materials.
“Without the highly parallel supercomputing resources and expertise at Brookhaven, it would have been nearly impossible to pinpoint this transition in strained monolayers,” Isaacs said.[Justin Eure, 631.344.2347,
jeure@bnl.gov]
