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APS » Journals » Phys. Rev. Lett. » Volume 102 » Issue 18
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Phys. Rev. Lett. 102, 185501 (2009) [4 pages]

Superhard Semiconducting Optically Transparent High Pressure Phase of Boron

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E. Yu. Zarechnaya1, L. Dubrovinsky1, N. Dubrovinskaia2,3, Y. Filinchuk4, D. Chernyshov4, V. Dmitriev4, N. Miyajima1, A. El Goresy1, H. F. Braun5, S. Van Smaalen3, I. Kantor6, A. Kantor6, V. Prakapenka6, M. Hanfland7, A. S. Mikhaylushkin8, I. A. Abrikosov8, and S. I. Simak8
1Bayerisches Geoinstitut, Universität Bayreuth, 95440 Bayreuth, Germany
2Mineralphysik, Institut für Geowissenschaften, Universität Heidelberg, 69120 Heidelberg, Germany
3Lehrstuhl für Kristallographie, Physikalisches Institut, Universität Bayreuth, 95440 Bayreuth, Germany
4Swiss-Norwegian Beam lines at ESRF, 38043 Gernoble, France
5Experimentalphysik V, Physikalisches Institut, Universität Bayreuth, 95440 Bayreuth, Germany
6GeoSoilEnviroCARS, University of Chicago, 5640 South Ellis, Chicago, Illinois 60637, USA
7ESRF, Boîte Postale 220, 38043 Grenoble, France
8Department of Physics, Chemistry and Biology, Linköping University, SE-581 33 Linköping, Sweden

Received 16 January 2009; published 7 May 2009

An orthorhombic (space group Pnnm) boron phase was synthesized at pressures above 9 GPa and high temperature, and it was demonstrated to be stable at least up to 30 GPa. The structure, determined by single-crystal x-ray diffraction, consists of B12 icosahedra and B2 dumbbells. The charge density distribution obtained from experimental data and ab initio calculations suggests covalent chemical bonding in this phase. Strong covalent interatomic interactions explain the low compressibility value (bulk modulus is K300=227  GPa) and high hardness of high-pressure boron (Vickers hardness HV=58  GPa), after diamond the second hardest elemental material.

© 2009 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.102.185501
DOI:
10.1103/PhysRevLett.102.185501
PACS:
61.66.−f, 61.50.Ks, 62.20.D−, 62.50.−p
 
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