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Phys. Rev. B 81, 020102(R) (2010) [4 pages]

Geometrical frustration in an elemental solid: An Ising model to explain the defect structure of β-rhombohedral boron

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Tadashi Ogitsu1,*, François Gygi2,3, John Reed1, Masafumi Udagawa4, Yukitoshi Motome4, Eric Schwegler1, and Giulia Galli1,5
1Condensed Matter and Materials Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94551, USA
2Center for Applied Scientific Computing, Lawrence Livermore National Laboratory, Livermore, California 94551, USA
3Department of Applied Science, University of California, Davis, California 95616, USA
4Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
5Department of Chemistry, University of California, Davis, California 95616, USA

Received 9 November 2009; revised 28 December 2009; published 25 January 2010

Recently, it was reported that β-rhombohedral boron has a negative defect formation energy, which explains the presence of a macroscopic amount (4 at. %) of intrinsic defects. In this work, it is shown that the defects in boron have geometrical frustration described by an antiferromagnetic Ising model on an expanded kagome lattice, which is responsible for the reported macroscopic residual entropy. We suggest that the reported anomalies in the transport properties of β-boron are due to the hopping of boron atoms between nearly degenerate configurations.

© 2010 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.81.020102
DOI:
10.1103/PhysRevB.81.020102
PACS:
61.66.Bi, 61.72.Bb, 64.60.De, 81.30.Dz

*ogitsu@llnl.gov

 
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