Electronic structures, total energies, and optical properties of. alpha. -rhombohedral B sub 12 and. alpha. -tetragonal B sub 50 crystals

Journal Article · Sun Mar 15 00:00:00 EST 1992 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.45.5895· OSTI ID:7281893

Li, D; Xu, Y; Ching, W Y ^[1]

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1. Department of Physics, University of Missouri Kansas City, Kansas City, Missouri 64110 (United States)

The band structures of {alpha}-rhombohedral B{sub 12} ({alpha}-{ital r}-B{sub 12}) and {alpha}-tetragonal B{sub 50} ({alpha}-{ital t}-B{sub 50}) crystals have been calculated by means of the first-principles orthogonalized linear combination of atomic orbitals method. It is shown that {alpha}-{ital r}-B{sub 12} is a semiconductor with an indirect band gap of 1.70 eV and {alpha}-{ital t}-B{sub 50} is a metal with a semiconductorlike band structure near the Fermi level. The intra-icosahedral and inter-icosahedral bondings in these two crystals are elucidated by resolving the density of states into various partial components, and by studying the valence-charge-density distributions. There is strong evidence for weak three-center bonding in the B crystals, but the traditional view regarding the bonding pattern in icosahedral B{sub 12} may be oversimplified. The total energies of {alpha}-{ital r}-B{sub 12} and {alpha}-{ital t}-B{sub 50} are calculated as a function of crystal volumes without change in the symmetry of the crystals. The equilibrium volume, the bulk moduli, and the cohesive energies obtained are in good agreement with available experimental data and some other recent calculations. Using the wave functions obtained from the band-structure calculation, the frequency-dependent interband optical conductivities in {alpha}-{ital r}-B{sub 12} and {alpha}-{ital t}-B{sub 50} crystals are also calculated. The real and imaginary parts of the dielectric-function curve are shown as a function of photon energy up to 40 eV for {alpha}-{ital r}-B{sub 12} and up to 10 eV for {alpha}-{ital t}-B{sub 50}. They are significant differences in the optical properties of these two crystals because of the different nature of the band structures. For {alpha}-{ital r}-B{sub 12}, a large plasmon excitation at 31 eV is predicted.

• DOE Contract Number: FG02-84ER45170
• OSTI ID: 7281893
• Journal Information: Physical Review, B: Condensed Matter; (United States), Vol. 45:11; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BORON
ELECTRONIC STRUCTURE
OPTICAL PROPERTIES
BONDING
CRYSTALS
ENERGY GAP
ENERGY-LEVEL DENSITY
FERMI LEVEL
TETRAGONAL LATTICES
CRYSTAL LATTICES
CRYSTAL STRUCTURE
ELEMENTS
ENERGY LEVELS
FABRICATION
JOINING
PHYSICAL PROPERTIES
SEMIMETALS
360606* - Other Materials- Physical Properties- (1992-)