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Phys. Rev. B 80, 060103(R) (2009) [4 pages]

Anisotropy of hardness from first principles: The cases of ReB2 and OsB2

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Antonín Šimůnek*
Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 53 Prague, Czech Republic

Received 7 August 2009; published 31 August 2009

See accompanying Physics Focus

The expression for hardness related to crystal orientation is proposed. Because all quantities in the equation are inherently coupled to the atomistic structure of matter, the anisotropy of hardness can be determined by first-principles methods. The calculations show the highest hardness is in ReB2 and OsB2 single crystals along the c axis, 50.3 and 45.5 GPa, respectively, and are in agreement with measurements. The presented model implies that hardness predominantly reflects the strength of bonds transversely oriented to the direction of indentation.

© 2009 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.80.060103
DOI:
10.1103/PhysRevB.80.060103
PACS:
62.20.Qp, 71.20.Be

*simunek@fzu.cz