Letter abstract


Nature Materials 3, 111 - 114 (2004)
doi:10.1038/nmat1060

Subject Category: Design synthesis and processing

The formation of sp3 bonding in compressed BN

Yue Meng1,2, Ho-kwang Mao2, Peter J. Eng3, Thomas P. Trainor3,5, Matthew Newville3, Michael Y. Hu1,2, Chichang Kao4, Jinfu Shu2, Daniel Hausermann1,2 and Russell J. Hemley2

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Attributed to their specific atomic bonding, the soft, graphite-like, hexagonal boron nitride (h-BN) and its superhard, diamond-like, cubic polymorph (c-BN) are important technological materials with a wide range of applications1. At high pressure and temperature, h-BN can directly transform to a hexagonal close-packed polymorph (w-BN)2 that can be partially quenched after releasing pressure. Previous theoretical calculations3, 4, 5 and experimental measurements (primarily on quenched samples)6, 7, 8, 9 provided substantial information on the transition, but left unsettled questions due to the lack of in situ characterization at high pressures. Using inelastic X-ray scattering to probe the boron and nitrogen near K-edge spectroscopy, here we report the first observation of the conversion process of boron and nitrogen sp2- and p-bonding to sp3 and the directional nature of the sp3 bonding. In combination with in situ X-ray diffraction probe, we have further clarified the structure transformation mechanism. The present archetypal example opens two enormous, element-specific, research areas on high-pressure bonding evolutions of boron and nitrogen; each of the two elements and their respective compounds have displayed a wealth of intriguing pressure-induced phenomena10 that result from bonding changes, including metallization11, 12, superconductivity13, 14, semiconductivity15, polymerization16 and superhardness2, 17, 18.

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  1. HPCAT, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
  2. Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015, USA
  3. GSECARS, University of Chicago, Chicago, Illinois 60439, USA
  4. National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973, USA
  5. Present address: Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, Alaska 99775, USA

Correspondence to: Yue Meng1,2 e-mail: ymeng@hpcat.aps.anl.gov

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