Prediction of a new ground state of superhard compound B6O at ambient conditions

Dong, Huafeng; Oganov, Artem R.; Wang, Qinggao; Wang, Shengnan; Wang, Zhenhai; Zhang, Jin; Esfahani, M. Mahdi Davari; Zhou, Xiang-Feng; Wu, Fugen; Zhu, Qiang

doi:10.1038/srep31288

Cited by 34 publications

(23 citation statements)

References 45 publications

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“…The enthalpy difference between these two structures is small (at ambient pressure it is only 1.8 meV per formula unit, and increases slightly with pressure). This prediction was published [12] and then our predicted Cmcm-B 6 O phase was experimentally confirmed [34].…”

Section: Resultssupporting

confidence: 58%

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Boron oxides under pressure: Prediction of the hardest oxides

et al. 2018

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We search for stable compounds of boron and oxygen at pressures from 0 to 500 GPa using the ab initio evolutionary algorithm USPEX. Only two stable stoichiometries of boron oxides, namely, B 6 O and B 2 O 3 , are found to be stable, in good agreement with experiment. A hitherto unknown phase of B 6 O at ambient pressure, Cmcm-B 6 O, has recently been predicted by us and observed experimentally. For B 2 O 3 , we predict three previously unknown stable high-pressure phases-two of these (Cmc2 1 and P 2 1 2 1 2 1) are dynamically and mechanically stable at ambient pressure, and should be quenchable to ambient conditions. Their predicted hardnesses, reaching 33-35 GPa, make them harder than SiO 2-stishovite. These are the hardest known oxides (if one disregards B 6 O, which is essentially a boron-based insertion compound). Under pressure, the coordination number of boron atoms changes from 3 to 4 to 6, skipping fivefold coordination.

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Section: Resultssupporting

confidence: 58%

“…Recently, yet another pure bulk modification of boron, τ -B [2], and two-dimensional (2D) allotropes of boron, borophenes, were identified [3,4]. Boron oxide B 2 O 3 and suboxide B 6 O are well established, but there are also controversial compounds proposed in the literature [4][5][6][7][8][9][10][11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Boron oxides under pressure: Prediction of the hardest oxides

et al. 2018

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“…Shear modulus of the B 6 O crystal is projected to be 227 GPa, agreeing with the available results of 207‐218 GPa in the literature. For the amorphous state the modulus is computed to be 86 GPa.…”

Section: Resultssupporting

confidence: 87%

“…Form these three equations, the Vickers hardness is projected to be about 34 GPa (Teter), 43 GPa (Chen), and 41 GPa (Tian) for the crystal structure, comparable with the experimental predictions of 38‐45 GPa . For the amorphous phase, on the other hand, we compute the Vickers hardness to be 13 GPa (Teter), 18 GPa (Chen) and 17 GPa (Tian).…”

Section: Resultssupporting

confidence: 62%

Amorphous boron suboxide

Durandurdu

2019

J Am Ceram Soc

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We study the atomic structure and the electronic and mechanical properties of amorphous boron suboxide (B 6 O) using an ab initio molecular dynamic technique. The amorphous network is attained from the rapid solidification of the melt and found to consist of boron and oxygen-rich regions. In the boron-rich regions, boron atoms form mostly perfect or imperfect pentagonal pyramid-like configurations that normally yield the construction of ideal and incomplete B 12 molecules in the model. In addition to the B 12 molecules, we also observe the development of a pentagonal bipyramid (B 7 ) molecule in the noncrystalline structure. In the oxygen-rich regions, on the other hand, boron and oxygen atoms form threefold and twofold coordinated motifs, respectively. The boron-rich and oxygen-rich regions indeed represent structurally the characteristic of amorphous boron and boron trioxide (B 2 O 3 ). The amorphous phase possesses a small band gap energy with respect to the crystal. On the bases of the localization of the tail states, we suggest that the p-type doping might be more convenient than the n-type doping in amorphous B 6 O. Bulk modulus and Vickers hardness of the noncrystalline configuration is estimated are be 106 and 13-18 GPa, respectively, which are noticeably less than those of the crystalline structure. Such a noticeable decrease in the mechanical properties is attributed to the presence of open structured B 2 O 3 glassy domains in the amorphous model. K E Y W O R D Samorphous, boron suboxide, hardness

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“…8 Carbon, which is widely used in industrial applications and scientic research, has numerous allotropes with abundant properties. Considering that B can combine O/C with strong covalent bonds in solid matter as B-O compounds, [9][10][11][12] and B-C compounds. [13][14][15] Inspired by that tP4-, and tI16-B 2 CO are both diamond-like structures, 4 oP8-B 2 CO is a lonsdaleite-like structure, 7 even the B 2 C X O (X $ 2) phases are also diamond-like structures and can be derived from different tP4-B 2 CO supercells with partial B and O replacing by C. 5 Hence, we are curious about that whether the fabricated B-C-O compounds with replacement of partial C atoms by B and O atoms in carbon allotropes are stable and what properties do they possess.…”

Section: Introductionmentioning

confidence: 99%