β-Rhombohedral Boron: At the Crossroads of the Chemistry of Boron and the Physics of Frustration

Ogitsu, Tadashi; Schwegler, Eric; Galli, Giulia

doi:10.1021/cr300356t

Cited by 185 publications

(152 citation statements)

References 274 publications

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“…Above 50 GPa the segregation of B 11 C p (CBC) into elemental carbon and boron becomes enthalpically preferred. In the pressure range examined boron undergoes two structural phase transitions (α → γ → α − Ga) [73][74][75][76][77][78][79] and carbon one (graphite → diamond) 80 . The pressures we calculate for these phase transitions, which are provided in the SI (Figs.…”

Section: Computational Details a Solid State Hugoniotmentioning

confidence: 99%

Properties of B4C in the shocked state for pressures up to 1.5 TPa

et al. 2017

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Density Functional Theory calculations using the quasi-harmonic approximation have been used to calculate the solid Hugoniot of two polytypes of boron carbide up to 100 GPa. Under the assumption that segregation into the elemental phases occurs around the pressure that the B11Cp(CBC) polytype becomes thermodynamically unstable with respect to boron and carbon, two discontinuities in the Hugoniot, one at 50 GPa and one at 90-100 GPa, are predicted. The former is a result of phase segregation, and the latter a phase transition within boron. First principles molecular dynamics (FPMD) simulations were employed to calculate the liquid Hugoniot of B4C up to 1.5 TPa, and the results are compared to recent experiments carried out at the Omega Laser Facility up to 700 GPa [Phys. Rev. B 94, 184107 (2016)]. A generally good agreement between theory and experiment was observed. Analysis of the FPMD simulations provides evidence for an amorphous, but covalently bound, fluid below 438 GPa, and an atomistic fluid at higher pressures and temperatures.

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Section: Computational Details a Solid State Hugoniotmentioning

confidence: 99%

Properties of B4C in the shocked state for pressures up to 1.5 TPa

et al. 2017

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“…10 This results in a variety of boron allotropes, which can be found in all-dimensions with diverse chemical and physical properties. [11][12][13][14][15] In addition to various low-dimensional allotropes, very recently Mannix et al 8 have grown the first atomically thin boron sheet on an Ag(111) substrate under ultrahigh-vacuum conditions. It has a buckled structure with triangular arrangement belonging to the Pmmn space group.…”

Section: Introductionmentioning

confidence: 99%

The interaction of halogen atoms and molecules with borophene

Khanifaev

Peköz

Konuk

et al. 2017

Phys. Chem. Chem. Phys.

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The realization of buckled monolayer sheets of boron (i.e., borophene) and its other polymorphs has attracted significant interest in the field of two-dimensional systems. Motivated by borophene's tendency to donate electrons, we analyzed the interaction of single halogen atoms (F, Cl, Br, I) with borophene. The possible adsorption sites are tested and the top of the boron atom is found as the ground state configuration. The nature of bonding and strong chemical interaction is revealed by using projected density of states and charge difference analysis. The migration of single halogen atoms on the surface of borophene is analyzed and high diffusion barriers that decrease with atomic size are obtained.The metallicity of borophene is preserved upon adsorption but anisotropy in electrical conductivity is altered. The variation of adsorption and formation energy, interatomic distance, charge transfer, diffusion barriers, and bonding character with the type of halogen atom are explored and trends are revealed. Lastly, the adsorption of halogen molecules (F 2 , Cl 2 , Br 2 , I 2 ), including the possibility of dissociation, is studied. The obtained results are not only substantial for fundamental understanding of halogenated derivatives of borophene, but also are useful for near future technological applications.

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“…Boron and related materials exhibit such extreme properties as low density, high hardness, high melting temperature, superconductivity, and ferromagnetism [1][2][3][4][5][6][7][8][9][10][11][12][13][14], making them candidates for such applications as high power electronics, superconductors, heat resistant alloys, coatings in nuclear reactors, body armor vests, abrasives, and cutting tool applications [7][8][9][10][11][12][13][14][15][16][17]. However, boron leads to quite complex structures arising from its unique bonding character that prefers formation of icosahedral shell complexes that stabilize 13 strong multicenter intraicosahedral bonds (requiring 26 electrons, Wade's rule).…”

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New Ground-State Crystal Structure of Elemental Boron

Reddy

Xie

et al. 2016

Phys. Rev. Lett.

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Elemental boron exhibits many polymorphs in nature based mostly on an icosahedral shell motif, involving stabilization of 13 strong multicenter intraicosahedral bonds. It is commonly accepted that the most thermodynamic stable structure of elemental boron at atmospheric pressure is the β rhombohedral boron (β-B). Surprisingly, using high-resolution transmission electron microscopy, we found that pure boron powder contains grains of two different types, the previously identified β-B containing a number of randomly spaced twins and what appears to be a fully transformed twinlike structure. This fully transformed structure, denoted here as τ-B, is based on the Cmcm orthorhombic space group. Quantum mechanics predicts that the newly identified τ-B structure is 13.8 meV=B more stable than β-B. The τ-B structure allows 6% more charge transfer from B 57 units to nearby B 12 units, making the net charge 6% closer to the ideal expected from Wade's rules. Thus, we predict the τ-B structure to be the ground state structure for elemental boron at atmospheric pressure. DOI: 10.1103/PhysRevLett.117.085501 Boron and related materials exhibit such extreme properties as low density, high hardness, high melting temperature, superconductivity, and ferromagnetism [1][2][3][4][5][6][7][8][9][10][11][12][13][14], making them candidates for such applications as high power electronics, superconductors, heat resistant alloys, coatings in nuclear reactors, body armor vests, abrasives, and cutting tool applications [7][8][9][10][11][12][13][14][15][16][17]. However, boron leads to quite complex structures arising from its unique bonding character that prefers formation of icosahedral shell complexes that stabilize 13 strong multicenter intraicosahedral bonds (requiring 26 electrons, Wade's rule). These complex structures make it difficult to interpret and understand the relationships between structure and properties. Indeed, even the ground state structure of boron has been controversial for over 30 years [6,[15][16][17].A number of crystalline structural forms for elemental boron have been discovered over the last two centuries [18][19][20]. However, only three phases correspond to pure boron: α-B 12 [18], β-B 105 [19], and γ-B 28 [20], with most of the others probably stabilized by impurities [21][22][23]. It has been long suspected that the β rhombohedral boron (β-B 105 ) structure is the most thermodynamic stable allotrope at low pressures [6,[15][16][17]. However, the quantum mechanics studies [15,16] predict that the α-B 12 structure is more stable than β-B 105 by 25.3 meV=atom, leading to a long debate of which phase is the ground state structure for elemental boron [6,[15][16][17]24]. Recent quantum mechanics studies have suggested that particular choices for the partial occupation sites in β-B 105 and including zero point motion might lead to an energy for β-B 105 that is more stable than α-B 12 structure at ambient conditions [16,25].Twinned structures have been observed in β-B 105 [26,27] and boron related materials such as ...

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β-Rhombohedral Boron: At the Crossroads of the Chemistry of Boron and the Physics of Frustration

Cited by 185 publications

References 274 publications

Properties of B4C in the shocked state for pressures up to 1.5 TPa

Properties of B4C in the shocked state for pressures up to 1.5 TPa

The interaction of halogen atoms and molecules with borophene

New Ground-State Crystal Structure of Elemental Boron

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