title: Superhard semiconducting optically transparent high pressure phase of boron.
abstract: 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.
authors.affiliation: Bayerisches Geoinstitut, Universität Bayreuth, 95440 Bayreuth, Germany.
authors.forename: E Yu
authors.initials: EY
authors.lastname: Zarechnaya
authors.forename: L
authors.initials: L
authors.lastname: Dubrovinsky
authors.forename: N
authors.initials: N
authors.lastname: Dubrovinskaia
authors.forename: Y
authors.initials: Y
authors.lastname: Filinchuk
authors.forename: D
authors.initials: D
authors.lastname: Chernyshov
authors.forename: V
authors.initials: V
authors.lastname: Dmitriev
authors.forename: N
authors.initials: N
authors.lastname: Miyajima
authors.forename: A
authors.initials: A
authors.lastname: El Goresy
authors.forename: H F
authors.initials: HF
authors.lastname: Braun
authors.forename: S
authors.initials: S
authors.lastname: Van Smaalen
authors.forename: I
authors.initials: I
authors.lastname: Kantor
authors.forename: A
authors.initials: A
authors.lastname: Kantor
authors.forename: V
authors.initials: V
authors.lastname: Prakapenka
authors.forename: M
authors.initials: M
authors.lastname: Hanfland
authors.forename: A S
authors.initials: AS
authors.lastname: Mikhaylushkin
authors.forename: I A
authors.initials: IA
authors.lastname: Abrikosov
authors.forename: S I
authors.initials: SI
authors.lastname: Simak