Ionic high-pressure form of elemental boron

Oganov, Artem R.; Chen, Jiuhua; Gatti, Carlo; Ma, Yanwei; Ma, Yanming; Glass, Colin W.; Liu, Zhenxian; Yu, Tony; Kurakevych, Oleksandr O.; Solozhenko, Vladimir L.

doi:10.1038/nature07736

Cited by 841 publications

(823 citation statements)

References 24 publications

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“…[46]. This trend that intericosahedral bond is shorter than intraicosahedral bond holds even for the recently discovered phase γ-boron [3,47]. Therefore, it is a common property for boron solids.…”

Section: Icosahedron-based Structurementioning

confidence: 92%

“…The term "ionicity" might be another important concept for understanding the physical and chemical properties of boron solids [135]. Recently, this concept attracts much attention in connection with successive discoveries of boron solids, such as γ-boron [3]. I apologize to readers for not providing deep insights into the role of ionicity in the material research, besides saying a plain thought that the ionicity is only a consequence of the structure but not the cause.…”

Section: Gap Problemmentioning

confidence: 96%

“…This is particularly interesting, by considering that the value is much smaller than that of α-rhombohedral boron (-17 meV/GPa), despite that the structure is different only in the presence of the C chain otherwise the same. A recently discovered high-pressure phase of boron, γ-orthorhombic boron, also has a very small value A g = -1 meV/GPa [3]. When we look at a low pressure region (< 10 GPa), the slope |A g | is less than 1 meV/GPa, and it seems even positive for the initial slope.…”

Section: Gap Problemmentioning

confidence: 99%

“…This is the hardest material ever reported, except diamond. Even in pure boron, a new polymorph of the highest density, γ-orthorhombic boron, has been discovered [2,3] and later confirmed [4]. Related to superhard materials, an epoch making event in this field is the discovery of superconductivity in boron at high pressure in 2001, although pure boron is a semiconductor [5].…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Electronic structures and mechanical properties of boron and boron-rich crystals (Part I)

Shirai

2010

J. Superhard Mater.

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Section: Icosahedron-based Structurementioning

confidence: 92%

Section: Gap Problemmentioning

confidence: 96%

Section: Gap Problemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Electronic structures and mechanical properties of boron and boron-rich crystals (Part I)

Shirai

2010

J. Superhard Mater.

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“…Table 3 Table 2. Present our results of Young's modulus (E), bulk modulus (B), shear modulus (G), and Poisson's ratio (υ) of polycrystalline γ-and β-B, respectively, in comparison with previous experimental and calculated results [2,6,14,17,19,22,24,25,[31][32][33]. Table 3.…”

mentioning

confidence: 99%

Polycrystalline γ-boron: As hard as polycrystalline cubic boron nitride

et al. 2012

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The Vickers hardness of polycrystalline γ-B was measured using a diamond indentation method. The elastic properties of polycrystalline γ-B were determined using ultrasonic measurement method. Under the loading force up to 20 N, our test gave an average Vickers hardness in the asymptotic-hardness region of 30.3 GPa. We also measured the hardness and elastic properties of polycrystalline β-B and PcBN for comparison. The hardness and elastic properties for polycrystalline γ-B was found to be very close to that of PcBN.

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Borides: Solid‐State Chemistry

Fokwa

2014

Encyclopedia of Inorganic and Bioinorganic Chemistry

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Boron forms compounds with most other elements. In addition to numerous binary and ternary compounds with metals—the true borides—boron forms related compounds with carbon, silicon, nitrogen, phosphorus, arsenic, oxygen, sulfur, and selenium. These related compounds are formed by elements more electronegative than boron and cannot therefore be denoted as borides. They display, however, similar properties and structures as borides, and are, therefore, included in this article. Borides are to some extent related to carbides and nitrides. All three groups of compounds are compounds between small nonmetal and larger metal atoms. They are occasionally denoted interstitial compounds, as the small nonmetal atoms often occupy the interstices between the metal atoms in metal‐rich compounds. In boron‐rich compounds, however, boron octahedra or icosahedra form a continuous three‐dimensional network. Most borides are characterized by high melting points, extreme hardness, brittleness, high chemical stability, and high inertness toward reactive metals. The borides are nonmolecular compounds and knowledge of the crystal structure is consequently of very high importance to characterize a boride phase. The structural principles of mainly the binary and ternary borides are described in this article. There are a total number of at least 1000 binary and ternary borides known at present. The chemical bonding in borides has evident contributions from covalent, ionic as well as metallic bonding, which explains some of the unique properties of the borides. As a rule, phases containing a large proportion of boron are semiconductors, whereas those with a lower proportion of boron are metallic conductors. TiB 2 and MgB 2 (superconductor below 39 K) are good metallic conductors, whereas MeB 6 phases are either semiconductors or metallic conductors depending on the metal. Many theoretical calculations are available, in particular of diborides, including the superconductor MgB 2 . The uses of borides and related compounds are mainly based on their hardness, chemical inertness, and magnetic and electrical properties. A few examples may be mentioned. B 4 C and cubic BN are used as abrasives, B 4 C and hexaborides as surface coatings, and CaB 6 as deoxidation agent in some metallurgical processes. TiB 2 is used in the production of vaporization boats for aluminum. It is also used in the industrial production process for aluminum owing to its high electrical conductivity and inertness toward liquid aluminum. Nd 2 Fe 14 B is, at room temperature, the strongest permanent magnetic material known. Large single crystals of YB 66 are used for monochromating synchrotron radiation.

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Ionic high-pressure form of elemental boron

Cited by 841 publications

References 24 publications

Electronic structures and mechanical properties of boron and boron-rich crystals (Part I)

Electronic structures and mechanical properties of boron and boron-rich crystals (Part I)

Polycrystalline γ-boron: As hard as polycrystalline cubic boron nitride

Borides: Solid‐State Chemistry

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