Lattice Constants of Boron Carbides

Aselage, T. L.; Tissot, Ralph G.

doi:10.1111/j.1151-2916.1992.tb04485.x

Cited by 118 publications

(93 citation statements)

References 21 publications

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“…The former model is evident mainly by ab initio calculations [16][17][18], where it is shown to have considerably lower energy as compared to B 11 C(BBC) [16,19]. Meanwhile, the latter model is consistent with the analyses of structural data from x-ray diffraction [20] and Raman spectra [21][22][23] of boron carbide at different at.% C in its single-phase region.…”

Section: Introductionsupporting

confidence: 66%

Configurational order-disorder induced metal-nonmetal transition inB13C2studied with first-principles superatom-special quasirandom structure method

et al. 2015

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Due to a large discrepancy between theory and experiment, the electronic character of crystalline boron carbide B 13 C 2 has been a controversial topic in the field of icosahedral boron-rich solids. We demonstrate that this discrepancy is removed when configurational disorder is accurately considered in the theoretical calculations. We find that while the ordered ground state B 13 C 2 is metallic, the configurationally disordered B 13 C 2 , modeled with a superatom-special quasirandom structure method, goes through a metal to nonmetal transition as the degree of disorder is increased with increasing temperature. Specifically, one of the chain-end carbon atoms in the CBC chains substitutes a neighboring equatorial boron atom in a B 12 icosahedron bonded to it, giving rise to a B 11 C e (BBC) unit. The atomic configuration of the substitutionally disordered B 13 C 2 thus tends to be dominated by a mixture between B 12 (CBC) and B 11 C e (BBC). Due to splitting of valence states in B 11 C e (BBC), the electron deficiency in B 12 (CBC) is gradually compensated.

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Section: Introductionsupporting

confidence: 66%

Configurational order-disorder induced metal-nonmetal transition inB13C2studied with first-principles superatom-special quasirandom structure method

et al. 2015

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“…Indicated by the first-principles-based total energy calculations [46][47][48], the model of B 12 (CBC) is shown to have considerably lower energy as compared to the B 11 C(BBC) unit, and thus often being discussed in the literature. The latter model is however consistent with the analyses of structural data from x-ray diffraction [49] and Raman spectra [50][51][52] of boron carbide at different at.% C in its single-phase region.…”

Section: Boron Carbidesupporting

confidence: 86%

First-principles study of configurational disorder in icosahedral boron-rich solids

Ektarawong¹

2015

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This thesis is a theoretical study of configurationally disordered icosahedral boronrich solids, in particular boron carbides, using density functional theory and alloy theory. The goal is to resolve discrepancies, regarding the properties of boron carbides, between experiments and previous theoretical calculations which have been a controversial issue in the field of icosahedral boron-rich solids. For instance, B 13 C 2 is observed experimentally to be a semiconductor, meanwhile electronic band structure calculations reveal a metallic character of B 13 C 2 due to its electron deficiency. In B 4 C, on the other hand, the experimentally observed band gap is unexpectedly smaller, not the usual larger, than that of standard DFT calculations. Another example is given by the existence of a small structural distortion in B 4 C, as predicted in theoretical calculations, which reduces the crystal symmetry from the experimentally observed rhombohedral (R3m) to the based-centered monoclinic (Cm). Since boron carbide is stable as a single-phase over a broad composition range (∼8-20 at.% C), substitution of boron and carbon atoms for one another is conceivable. For this reason, the discrepancies have been speculated in the literature, without a proof, to originate from configurational disorder induced by substitutional defects. However, owing to its complex atomic structure, represented by 12-atom icosahedra and 3-atom intericosahedral chains, a practical alloy theory method for direct calculations of the properties of the relevant configurations of disordered boron carbides, as well as for a thermodynamic assessment of their stability has been missing.In this thesis, a new approach, the superatom-special quasirandom structure (SA-SQS), has been developed. The approach allows one to model configurational disorder in boron carbide, induced by high concentrations of low-energy B/C substitutional defects. B 13 C 2 and B 4 C are the two stoichiometries, mainly considered in this study, as they are of particular importance and have been in focus in the literature. The results demonstrate that, from thermodynamic considerations, both B 13 C 2 and B 4 C configurationally disorder at high temperature. In the case of B 13 C 2 , the configurational disorder splits off some valence states into the band gap that in turn compensates the electron deficiency in ordered B 13 C 2 , thus resulting in a semiconducting character. As for B 4 C, the configurational disorder eliminates the monoclinic distortion, thus resulting in the restoration of the higher rhombohedral symmetry. Configurational disorder can also account for an exceliii iv lent agreement on elastic moduli of boron carbide between theory and experiment. Thus, several of the previous discrepancies between theory and experiments are resolved.Inspired by attempts to enhance the mechanical properties of boron suboxide by fabricating boron suboxide-boron carbide composites, as recently suggested in the literature, the SA-SQS approach is used for modeling mixtures of boron sub...

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“…Generally these different polytypes have been associated with changing composition such as increasing the boron concentration [3,4,6,10,[24][25][26][27][28][29][30][31][32][33][34] or replacing carbon with other main group elements such as phosphorus [35,36], aluminium [37][38][39][40][41] and other main group elements. We have identified different polytypes of the semiconducting boron carbides with large direct band gaps (materials formed from para-carborane and dimeric phosphorus bridged ortho-carborane (C 2 B 10 H 10 PCl) 2 ) and those with smaller band gaps (materials formed from ortho-carborane and meta-carborane).…”

mentioning

confidence: 99%

Evidence for multiple polytypes of semiconducting boron carbide (C₂B₁₀) from electronic structure

Popa¹,

Brand²,

Balaz³

et al. 2005

J. Phys. D: Appl. Phys.

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Lattice Constants of Boron Carbides

Cited by 118 publications

References 21 publications

Configurational order-disorder induced metal-nonmetal transition inB13C2studied with first-principles superatom-special quasirandom structure method

Configurational order-disorder induced metal-nonmetal transition inB13C2studied with first-principles superatom-special quasirandom structure method

First-principles study of configurational disorder in icosahedral boron-rich solids

Evidence for multiple polytypes of semiconducting boron carbide (C₂B₁₀) from electronic structure

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Lattice Constants of Boron Carbides

Cited by 118 publications

References 21 publications

Configurational order-disorder induced metal-nonmetal transition inB13C2studied with first-principles superatom-special quasirandom structure method

Configurational order-disorder induced metal-nonmetal transition inB13C2studied with first-principles superatom-special quasirandom structure method

First-principles study of configurational disorder in icosahedral boron-rich solids

Evidence for multiple polytypes of semiconducting boron carbide (C2B10) from electronic structure

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Evidence for multiple polytypes of semiconducting boron carbide (C₂B₁₀) from electronic structure