Electronic structures and optical properties of low- and high-pressure phases of crystallineB2O3

Abstract

The high-and low-pressure phases of crystalline boron oxide B 2 O 3 are investigated by first-principle calculations using a local-density approximation ͑LDA͒. Both phases are insulators with wide LDA band gaps of 6.20 eV for B 2 O 3 -I ͑low pressure͒ and 8.85-eV for B 2 O 3 -II ͑high pressure͒. The total density of states are calculated and resolved into atomic and orbital components. The bond strength and charge transfers in these two crystals are investigated by calculating the overlap populations and Mulliken effective charges. B 2 O 3 -II is found to be more ionic than B 2 O 3 -I. It is also concluded that the sp 2 planar bonding in B 2 O 3 -I is stronger than the sp 3 tetrahedral bonding in B 2 O 3 -II. The optical conductivities, the dielectric functions, and the energy-loss functions are also calculated using the wave functions at a large number of k points in the Brillouin zone. The calculated static dielectric constants for B 2 O 3 -I and B 2 O 3 -II are 2.32 and 2.35, respectively. The gross features of the optical spectra for the two crystals are quite similar with one marked difference. The B 2 O 3 -II crystal shows substantial optical anisotropy while B 2 O 3 -I is optically more isotropic. ͓S0163-1829͑96͒03143-8͔

Planar tunneling spectroscopy of the topological Kondo insulator SmB6

“…8(c). While the formation of some samarium oxides such as Sm 2 O 3 can't be completely ruled out due to their chemical complexity 59 , we think that the B 2 O 3 layer serves as a tunnel barrier, as also supported by a band structure calculation 60 showing that B 2 O 3 has a large (6-9 eV) band gap.…”

Mechanism of atomic diffusion in liquidB2O3: Anab initiomolecular dynamics study

“…While there have been reported several density-functional or Hartree-Fock studies for crystalline [8][9][10][11] and vitreous 12-14 B 2 O 3 so far, the liquid properties have not been investigated yet based on first-principles theories. The purpose of our study is to clarify the microscopic mechanism of atomic diffusion in the liquid state from first principles.…”

High pressure X-ray diffraction study on icosahedral boron arsenide (B12As2)

“…Consequences of the unusual structure include high stability, pressure-induced metallization, structure distortion [5][6][7][8][9], and superconductivity under extreme conditions [10][11]. Compared with pure boron, boron-rich compounds possess similar, but more complex, structures, which produce more interesting properties along with the similar stability exhibited in boron [12][13][14][15][16]. As a member of the boron-group compounds, boron arsenide (B 12 As 2 ) has a relatively complicated structure, and exhibits physical properties such as high hardness and high melting temperature due to its strong bonding [1,17].…”