September AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | S E P T E M B E R 2 0 1 8 1 2 MACHINE LEARNING PREDICTS MATERIAL PROPERTIES Researchers at Lawrence Liver- more National Laboratory (LLNL), the University of Nevada−Las Vegas, Stony Brook University, and UC Davis devised a method capable of combing through the vast space and potential arrange- ments of atoms in grain boundaries and predicting how they will interact under certain conditions. Scientists say the new technique, based on evolution- ary algorithms and machine learning, finally provides a way to predict mate- rial properties and could lead to major breakthroughs in developing materials with greater strength, more heat resis- tance, or higher conductivity. “What we developed is the first- of-its-kind computational tool that ef- fectively samples possible structures of grain boundaries and finds low-energy structures as well as important meta- stable states,” says principal investi- gator Timofey Frolov of LLNL. “What’s surprising and shocking is that we thought we understood the structures of boundaries, but we don’t. Basical- ly, we start from scratch now because many boundaries we look at have a dif- ferent structure fromwhat we previous- ly thought.” The work could have a significant impact on designing materials for a broad range of energy applications in- cluding solid state fuel cells, thermo- electrics, oxygen sensors, optical fibers, switches, laser amplifiers, and lenses, say scientists. Researchers created and characterized the newmodel using cop- per and successfully demonstrated and tested it with silicon, tungsten, and oth- er materials. The method is already be- ing implemented within LLNL’s fusion energy program. llnl.gov. NEW SUPERHARD MATERIAL DEBUTS An international team of scientists at the Moscow Institute of Physics and Technology (MIPT) has predicted a new superhard material that can be used in drilling, machine building, and other applications. The team reports that the new tungsten boride they discovered outperforms the widely used pobedit, a hard tungsten carbide and cobalt com- posite material with artificial diamond interspersed. The researchers at MIPT, in collaboration with scientists from the Skolkovo Institute of Science and Technology (Skoltech), Moscow, used their USPEX evolutionary algorithm to predict the new material, WB5, which can be synthesized at normal pressure. They say that WB5 can successfully compete with pobedit in the two most A new nanolaser employs the same color- changing mechanism that a chameleon uses to camouflage its skin. EMERGING TECHNOLOGY In June, the DOE’s Oak Ridge National Laboratory, Tenn., debuted Summit as the world’s smartest and most powerful scientific supercomputer. With a peak performance of 200,000 trillion calculations per second (200 petaflops), Summit will be eight times more powerful than America’s current top-ranked system, Titan, also housed at ORNL. energy.gov. BRIEF essential parameters—hardness and fracture toughness—which are 50% higher and 20% lower, respectively. www.mipt.ru.en . NEW NANOLASERS MIMIC CHAMELEONS A research team at Northwestern University, Evanston, Ill., developed a novel nanolaser that changes colors using the same mechanism as chame- leons. The work could enable advances in flexible optical displays in smart- phones and televisions, wearable pho- tonic devices, and ultrasensitive sen- sors that measure strain. In the same way a chameleon controls the spacing of nanocrystals on its skin, the new la- ser exploits periodic arrays of metal nanoparticles on a stretchable polymer matrix. As the matrix either stretches to pull the nanoparticles farther apart or contracts to push them closer togeth- er, the wavelength emitted from the laser changes, which also transforms its color. The resulting laser is robust, tunable, reversible, and has a high sen- sitivity to strain—critical properties for applications in responsive optical dis- plays. northwestern.edu . From left, Robert Rudd, Timofey Frolov, and Amit Samanta pose with a simulation of material crystallites separated by grain boundaries.