The Unusually Stable B<sub>100</sub>Fullerene, Structural Transitions in Boron Nanostructures, and a Comparative Study of α- and γ-Boron and Sheets

Özdoğan, Cem; Mukhopadhyay, Saikat; Hayami, Wataru; Güvenç, Zi̇ya B.; Pandey, Ravindra; Boustani, İhsan

doi:10.1021/jp911641u

Cited by 158 publications

(92 citation statements)

References 105 publications

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“…As an another stability measure, we compute HOMO-LUMO energy gap (E g ) [43][44][45] and they are given in Table 1. The lowest energy isomers B In Table 2, we give the binding energies per atom, the band gaps and NICS values of the well known α-B [12]. In accordance with the previous results [31], we found that B 80 buckyball has higher E b than V-B 80 and they have antiaromatic NICS values which are given as 10.5 ppm and 22.9 ppm respectively.…”

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confidence: 84%

A new hole density as a stability measure for boron fullerenes

Polad

Özay

2013

Phys. Chem. Chem. Phys.

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We investigate the stability of boron fullerene sets B76, B78 and B82. We evaluate the ground state energies, nucleus-independent chemical shift (NICS), the binding energies per atom and the band gap values by means of first-principles methods. We construct our fullerene design by capping of pentagons and hexagons of B60 cage in such a way that the total number of atoms is preserved. In doing so, a new hole density definition is proposed such that each member of a fullerene group has a different hole density which depends on the capping process. Our analysis reveal that each boron fullerene set has its lowest-energy configuration around the same normalized hole density and the most stable cages are found in the fullerene groups which have relatively large difference between the maximum and the minimum hole densities. The result is a new stability measure relating the cage geometry characterized by the hole density to the relative energy.The geometric structure of boron allotropes in respect to their ground state energy is a subject of great interest. Studies focused on searching the lowest energy configurations has yielded a variety of stable boron structures due to electron deficient nature of boron. Such structures involve molecular wheels [1,2], boron sheets composed of triangular and hexagonal motifs [3][4][5][6][7][8][9][10][11][12] [17,18]. Boron based forms are known for their complex chemistry. Unlike carbon, both pure boron and many boron rich compounds contain B 12 cage structures in their crystalline state. Furthermore, boron crystals show peculiarities such as uncommon 2c-1e and 3c-2e bonding [19] and unique aromaticity [20,21]. Most crystal samples exhibit defects, vacancies and interstitials, due to the flexible bond structure [22]. Among such structures, the newest form, orthorhombic γ-B 28 , is found to be the second hardest elemental material after diamond with a value of 58 GPa [23,24] and has strong covalent interatomic interactions even higher than the intraicosahedral bonds [25].A key concept in stability analysis of boron sheets is the hole density. This is defined as the ratio of the number of hexagonal holes to the number of atoms in the triangular sheet. The so called α-sheet was found to be the most stable boron sheet with η=1/9 [10]. In a recent work, it is shown that hexagonal holes of α-sheet are the scavengers of extra electrons from the filled hexagons [26]: a unique aspect of α-sheet, in conjunction with the hole density, is that the ratio η=1/9 exactly corresponds to the ratio of the extra π electron to the number of σ electrons in a filled hexagon. Boron layers composed of hexagonal hole doped triangular lattices manifest polymorphism [27] i.e. multiple 2D boron layers have comparable stabilities even some of them have lower energy than the α sheet [28,29]. Boron sheets g(1/8), g(2/15), α 1 and α 2 are the examples of such ground state structures. Such correlation between the

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confidence: 84%

A new hole density as a stability measure for boron fullerenes

Polad

Özay

2013

Phys. Chem. Chem. Phys.

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“…These calculations suggest that the π sheet is stable up to 1800 K and only small buckling vibration, following the normal phonon mode, occurs with temperatures below 1800 K. Thus, the π sheet is a kinetically trapped, highly stable metastable polymorph. At 1800 K, the structure undergoes a phase transition and form the previously reported χ 3 structure 5,11,12 (see Figure 2d), which is theoretically proven to be one of the most stable boron monolayer and has been prepared on a Ag(111) surface recently. 5 This phase is 0.05 eV/ B atom more stable than the π phase without support.…”

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confidence: 55%

Prediction of Two-Dimensional Phase of Boron with Anisotropic Electric Conductivity

Cui

Jimenez−Izal

Alexandrova

2017

J. Phys. Chem. Lett.

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Two-dimensional (2D) phases of boron are rare and unique. Here we report a new 2D all-boron phase (named the π phase) that can be grown on a W(110) surface. The π phase, composed of four-membered rings and six-membered rings filled with an additional B atom, is predicted to be the most stable on this support. It is characterized by an outstanding stability upon exfoliation off of the W surface, and unusual electronic properties. The chemical bonding analysis reveals the metallic nature of this material, which can be attributed to the multicentered π-bonds. Importantly, the calculated conductivity tensor is anisotropic, showing larger conductivity in the direction of the sheet that is in-line with the conjugated π-bonds, and diminished in the direction where the π-subsystems are connected by single σ-bonds. The π-phase can be viewed as an ultrastable web of aligned conducting boron wires, possibly of interest to applications in electronic devices.

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“…Starting from a bi-dimensional repetition of equilateral triangles, a plethora of such 2D structures have been predicted [1][2][3][4][5] by increasing the ratio of hexagon holes to the number of atomic sites in the original triangular sheet within one unit cell, namely, the hexagonal vacancy density η. Plus, a relationship among the vacancy density, the stability, and the morphology of boron sheets has been abduced [1][2][3][4][5][6] .…”

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confidence: 99%

Thermomechanical analysis of two-dimensional boron monolayers

Tsafack

Yakobson

2016

Phys. Rev. B

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Using density functional theory calculations (both perturbed and unperturbed) as well as thermodynamic and ballistic transport equations, what follows investigates thermal and mechanical properties of 2D boron monolayers (δ 6 -, α-, δ 5 -, and χ 3 -sheets with respective vacancy densities η = 0, 1/9, 1/7, 1/5) as they relate to the vacancy density. The triangular (δ 6 ) sheet's room-temperature phonon and electron thermal conductances are found to respectively be roughly 2.06 times and 6.60 times greater than those of PACS numbers: 65.40.-b, 62.20.-x, 63.22.-m

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The Unusually Stable B₁₀₀Fullerene, Structural Transitions in Boron Nanostructures, and a Comparative Study of α- and γ-Boron and Sheets

Cited by 158 publications

References 105 publications

A new hole density as a stability measure for boron fullerenes

A new hole density as a stability measure for boron fullerenes

Prediction of Two-Dimensional Phase of Boron with Anisotropic Electric Conductivity

Thermomechanical analysis of two-dimensional boron monolayers

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The Unusually Stable B100Fullerene, Structural Transitions in Boron Nanostructures, and a Comparative Study of α- and γ-Boron and Sheets

Cited by 158 publications

References 105 publications

A new hole density as a stability measure for boron fullerenes

A new hole density as a stability measure for boron fullerenes

Prediction of Two-Dimensional Phase of Boron with Anisotropic Electric Conductivity

Thermomechanical analysis of two-dimensional boron monolayers

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Product

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The Unusually Stable B₁₀₀Fullerene, Structural Transitions in Boron Nanostructures, and a Comparative Study of α- and γ-Boron and Sheets