b'Carnegie Science|Fall 2020 7Superdiamond Carbon-Boron CagesFinally SynthesizedCarnegies Gustav M. Borstad, Hanyu Liu, Piotr A. Guka, Michael Guerette, Juli-Anna Dolyniuk, Yue Meng, and Ronald Cohen, as well as University of Chicagos Eran Greenberg and Vitali Prakapenka and the U.S. Naval Research Laboratorys Brian L. Chaloux and Albert Epshteynapproached the problem by combining computations and experiments. We used advanced structure-searching tools to predict the first thermodynamically stable carbon-based clathrate and then synthesized the clathrate structure, which is comprised of carbon-boron cages that trap strontium atoms, under high-pressure and high-temperature conditions, Zhu said.The result is a 3-D, carbon-based framework with diamond-like bonding This structure, called the bipartite sodalite type clathrate, consists of truncated octahedral host cages that trapthat is recoverable to ambient conditions. strontium guest atoms. It was synthesized under high-pressure and high-temperature conditions using a laser- But unlike diamond, the strontium atoms heating technique. Image courtesy Tim Strobel, Carnegie Institution for Science trapped in the cages make the material metallicmeaning it conducts electricityA long-sought-after class of superdiamondwith potential for superconductivity at carbon-based materials with tunablehigh temperatures.mechanical and electronic properties wasWhats more, the properties of the predicted and synthesized by Carnegies Liclathrate can change depending on the Zhu and Timothy Strobel. Such a materialtypes of guest atoms within the cages. has not been synthesized until now. ScienceThe trapped guest atoms interact Advances strongly with the host cages, Strobelpublished the work. Carbon is the fourth most abundantremarked. Depending on the specific guest element in the universe and is fundamentalatoms present, the clathrate can be tuned to life as we know it. It is unrivaled in itsCarnegies Timothy Strobel (left) and Li Zhu (right), withfrom a semiconductor to a superconductor, ability to form stable structures, alone andtheir team, were the first to synthesize the long-sought- all while maintaining robust, diamond-like after carbon-based clathrates. The Journal of Physics: with other elements.Condensed Matter named Strobel as a 2019 emergingbonds. Given the large number of possible A materials properties are determinedleader, identifying him as one of the most excitingsubstitutions, we envision an entirely new by how its atoms are bonded and theresearchers of their generation, with the potential toclass of carbon-based materials with highly revolutionise their fields.structural arrangements that these bondsImage courtesy Carnegie Institution for Science tunable properties.create. For carbon-based materials, the typeFor anyone who is intoor whose kids of bonding makes the difference between thenumerous predictions of potentiallyare intoPokmon, this carbon-based hardness of diamond, which has three- synthesizable structures with this kind ofclathrate structure is like the Eevee of dimensional sp 3bonds, and the softness ofbonding, Strobel explained. Following amaterials, joked Zhu. Depending which graphite, which has two-dimensional sp 2 chemical principle that indicates addingelement it captures, it has different abilities.bonds, for example.boron into the structure will enhance its Despite the enormous diversity ofstability, we examined another 3-D-bonded carbon compounds, only a handful ofclass of carbon materials called clathrates,SUPPORT:three-dimensionally, sp 3 -bonded carbon- which have a lattice structure of cages thatDARPA supported this work. The Energy Frontier Research in Extreme Environments (EFree) Center, an Energy Frontier based materials are known, includingtrap other types of atoms or molecules.Research Center funded by the U.S. Department of Energy (DOE), Office of Science; the Polish National Agency for diamond. The three-dimensional bondingClathrates comprised of otherAcademic Exchange; the Warsaw University of Technology; a European Research Council Advanced Grant; and ToMCaT structure makes these materials veryelements and molecules are common andprovided additional support. Computations were conducted attractive for many practical applicationshave been synthesized or found in nature.using the supercomputer Copper of U.S. Department of Defense HPCMP Open Research Systems and the Memex cluster of the because of their strength, hardness, andHowever, despite long-standing predictionsCarnegie Institution for Science. Portions of this work were performed at HPCAT and GeoSoilEnviroCARS, Advanced Photon thermal conductivity.of their existence, carbon-based clathratesSource, Argonne National Laboratory. HPCAT operations are Aside from diamond and some of itshave not been synthesized until now.supported by DOE-NNSAs Office of Experimental Sciences. GeoSoilEnviroCARS is supported by the National Science analogs that incorporate additional elements,Researchers have attempted to create themFoundation-Earth Sciences (EAR-1634415) and DOE-GeoSciences. The Advanced Photon Source is a DOE Office of almost no other extended sp 3carbonfor more than 50 years.Science User Facility operated for the DOE Office of Science by materials have been created, despiteStrobel, Zhu, and their team Argonne National Laboratory.'