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Title: Superhard Semiconducting Optically Transparent High Pressure Phase of Boron

Journal Article · · Phys. Rev. Lett.

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 B{sub 12} icosahedra and B{sub 2} 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 K{sub 300} = 227 GPa) and high hardness of high-pressure boron (Vickers hardness H{sub v} = 58 GPa), after diamond the second hardest elemental material.

Research Organization:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Organization:
USDOE
OSTI ID:
1005606
Journal Information:
Phys. Rev. Lett., Vol. 102, Issue (18) ; 05, 2009; ISSN 0031-9007
Country of Publication:
United States
Language:
ENGLISH