pp 683-690 | (1975) ‘Use of energy derivative of the radial solution in an augmented plane wave method: application to copper’, J. Phys. An analysis of the structure of tetragonal boron, as determined by H O A R D , and S A N D S , has been made in terms of the resonating-valence-bond theory. Herein, evolutionary structure searches performed at 100 GPa have uncovered a series of potential new metastable phases of boron, and bonding analyses were carried out to elucidate their electronic structure. Roy. This process is experimental and the keywords may be updated as the learning algorithm improves. These polymorphs, dynamically stable at 100 GPa, were grouped into two families. The absorption edges, photoeffects related to gap states, IR-active lattice vibrations and plasma vibrations are discussed with respect to band structure models, band structure calculations, and structure conceptions. Polarization studies have resulted in symmetry assignments for most of the Raman bands of α‐rhombohedral boron. Morosin, B. Mullendore, A. W., Emin, D. and Slack, G. A. Less Common Metals 82, 1–20. These materials are very stable and have exceptionally high melting points because the bonding between icosahedra is as strong, if not stronger, than the bonding within an icosahedron. ), Boron Rich Solids, American Institute of Physics Conference Proceedings 231, New York pp. Solid State 26, 114-6. van Schilfgaarde, M. and Harrison, W. A. Lee, S., Bylander, D. M. and Kleinman, L. (1990) ‘Bands and bonds of B12’, Phys. b, A fragment of the -rhombohedral boron structure. Over 10 million scientific documents at your fingertips. At smaller lattice constants, orbitals(bands) associated with bonds to adjacent icosahedra are lowered and orbitals(bands) associated with “antibonds” are raised. Abstract. Jansen, H. J. F. and Freeman, A. J. Full Record; Other Related Research Bouckaert, L. P., Smoluchowski, R., Wigner, E. (1936) ‘Theory of Brillouin zones and symmetry properties of wave functions in crystals’, Phys. It has five equilateral triangular faces meeting at each vertex. This site explores the structure and behavior of icosahedral boron-rich solids. Boron rich solids exhibit a fascinating geometric and electronic structure, unique in the periodic table. It is interesting to note here that the octahedron and icosahedron are different phases of the Jitterbug motion. Hexagonal boron nitride (hBN) is a promising material for a range of applications including deep-ultraviolet light emission. According to quantumchemical calculations the boron buckyball, B 80, is very similar to the buckminsterfullerene carbon analogue. -boron Weyrich, K. H., Brey, L. and Christensen, N. E. (1988) ‘Full-potential linear-muffin-tin-orbital calculation of phonon frequencies in semiconductors’, Phys. The structure of metallic superconducting boron is unknown. Armstrong, D. R., Bolland, J. and Perkins, P. G. (1984) ‘The electronic structure of a-B12, B. Bullett, D. W. (1983) ‘Electronic structure studies of boron and boron-rich borides’, in D. Emin, T. Aselage, C. L. Beckel, I. Part of Springer Nature. Reliable previous optical absorption spectra are extended by new results e.g. OSTI.GOV Journal Article: Lattice vibrations of the icosahedral solid. Another kind of prominent peak on the external B B bonds of the icosahedron indicated that the inter-icosahedral B B bonds are two-center bonds. Your email address will not be published. Rev. constitutes 15 crystallographically independent atomic sites and these are fully occupied. Cite as. Switendick, A. C. and Morosin, B. For crystalline lattice constants greater than 1.25 times the equilibrium one, band overlap occurs with concomitant metallic behavior. The structure of boron carbides is similar to icosahedral boron pnictides except they have a three-atom chain along the longest diagonal of each rhombohedral cell in place of the chain of two pnictides atoms.6 The three-atom chain are thought of as C-B-C, C-B-B, or B-B-B. Longuett-Higgins, H. C. and Roberts, M. de V. (1955) ‘The electronic structure of an icosahedron of boron atoms’, Proc. Both allotropes have a truncated icosahedral structure, which in the case of boron is complemented by an additional set of 20 boron atoms, capping the 20 hexagonal faces.1 The HOMO and LUMO of icosahedral B X-ray difference electron densities in α-AlB 12 were examined. One-dimensional icosahedral boron chains and two-dimensional icosahedral boron sheets (icosahedral α, δ 6, and δ 4 sheets) that contain icosahedra B 12 as their building units An icosahedron nests within an octahedron. Geometrically, polynuclear borane anions have trigonal faces. Each of the 12 edges of the octahedron correspond to the 12 vertices of the icosahedron. This is a preview of subscription content, Lipscomb, William N. (1981) ‘Borides and boranes’, J. Boron‐rich molecules and solids hold a special place within chemistry. These 12-atom groups make up an icosahedron, with one boron atom at each of its twelve vertices. The electronic structure of a regular icosahedron of boron atoms is investigated theoretically by the method of molecular orbitals. Both have icosahedral symmetry. Boron carbide (BC), due to its extreme hardness, low density, and demonstrated performance, has been used as an armor ceramic for many years [1]. Low-dimensional boron structures based on icosahedron B12 C B Kah1,MYu1, P Tandy1,2, C S Jayanthi1 and S Y Wu1 1Department of Physics and Astronomy, University of Louisville, Louisville, Kentucky, 40292, USA 2Defense Threat Reduction Agency, 8725 John J Kingman Rd, Stop 6201, Fort Belvoir, VA, 22060, USA E-mail: m0yu0001@louisville.edu Received 19 March 2015, revised 7 August 2015 The electronic structure of icosahedral boron clusters. These 12-atom groups make up an icosahedron, with one boron atom at each of its twelve vertices. A. Howard and C. Wood (eds. Download PDF Download Full PDF Package. A short summary of this paper. Icosahedral Boron-Rich Solids as Refractory Semiconductors - Volume 97 - David Emin This paper. There are not a sufficient number of valence electrons in the boron atoms for conventional covalent bonding to occur because each boron atom is bonded to five other boron atoms. Michel Deza. (1991) ‘Electronic structures, total energies and optical properties of a-rhombohedral B12 and a-tetragonal B50 crystals’, preprint. 23, 2004-10. 7 shows the crystal structure of α - and β-boron along with that of boron carbide.The basic unit of boron is the all-boron icosahedra shown at the bottom of α-boron in Fig. The crystal structures of several icosahedral boron containing compounds have been refined using Mo Kα intensity data. These keywords were added by machine and not by the authors. Soc. (1971) Chemical Applications of Group Theory, WileyInterscience, New York. (1986) ‘Rhombohedral crystal structure of compounds containing boron-rich icosahedra’, in D. Emin, T. Aselage, C. L. Beckel, I. Create a free website or blog at WordPress.com. (1991) ‘Electronic charge density and bonding in a-boron: An experimental-theoretical comparison’ in D. Emin, T. L. Aselage, A. C. Switendick, B. Morosin and C. L. Beckel (eds. A. Howard and C. Wood (eds. Li, D., Xu, Y-N. and Ching, W. Y. is a dianion and bicapped square antiprism closo structure and B12H12 2 dianion has icosahedral closo geometry. 89, 6815-22. A neutral metallaborane comprising a Rh 4 B 12 polyhedron with icosioctahedron geometry with 16 vertices and 28 triangular faces was prepared (see structure; Rh: red, B: green). The spectra of α‐rhombohedral boron, boron arsenide, and boron phosphide are consistent with highly‐ordered materials. Not logged in Solov’ev, N. E., Averbakh, E. M. and Ugai, Ya. The carbon concentration of these materials ranges from 10% to 20% as defined by B12+x C3-x with 0.1
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