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First-Principles Investigations of the Structure, Electronic, and Optical Properties of Mullite-Type Orthorhombic Bi2M4O9 (M = Al3+, Ga3+)

Zahedi, E; Xiao, B; Shayestefar, M; (2016) First-Principles Investigations of the Structure, Electronic, and Optical Properties of Mullite-Type Orthorhombic Bi2M4O9 (M = Al3+, Ga3+). Inorganic Chemistry , 55 (10) pp. 4824-4835. 10.1021/acs.inorgchem.6b00330. Green open access

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Abstract

The structure, electronic band structure, density of state, projected wave function, and optical properties of mullite-type orthorhombic Bi2M4O9 (M = Al3+, Ga3+) crystals have been studied by applying density functional theory based on the Vanderbilt ultrasoft pseudopotential in the frame of the generalized gradient approximation as an exchange–correlation function. Satisfactory agreement between experimental and theoretical results indicates that the used method and conditions are suitable. M–O bonds in tetrahedral MO4 environments are stronger and more covalent with respect to octahedral MO6; also Bi–O bonds in both studied structures are almost ionic in nature. The photocatalytic activity of Bi2Al4O9 and Bi2Ga4O9 is enhanced due to unequal values of Mulliken charges on the O atoms in MO4, MO6, and BiO6E groups. Bi2Al4O9 and Bi2Ga4O9 are direct and indirect band gap semiconductors with band gaps of 2.71 and 2.86 eV, respectively. Higher photocatalytic activity of Bi2Al4O9 is inferable from the lower effective masses of photogenerated carriers around the conduction band minimum and valence band maximum, in comparison with Bi2Ga4O9. The presence of M and O orbitals in the valence and conduction bands reveals that symmetry breaking in the MO4 and MO6 units has an important role in separating charges and increasing photocatalytic activity. Photocatalytic activities of Bi2Al4O9 and Bi2Ga4O9 for decomposition of organic pollutants and generation of hydrogen from water splitting are confirmed from band edge potentials.

Type: Article
Title: First-Principles Investigations of the Structure, Electronic, and Optical Properties of Mullite-Type Orthorhombic Bi2M4O9 (M = Al3+, Ga3+)
Open access status: An open access version is available from UCL Discovery
DOI: 10.1021/acs.inorgchem.6b00330
Publisher version: http://dx.doi.org/10.1021/acs.inorgchem.6b00330
Language: English
Additional information: Copyright © 2016 American Chemical Society
Keywords: Science & Technology, Physical Sciences, Chemistry, Inorganic & Nuclear, Chemistry, Molecular Wave Functions, Photocatalytic Properties, Population Analysis, Elastic Properties, Bi2Fe4O9 Crystals, Thermal-Expansion, Single-Crystals, 1St Principles, Bi2Ga4O9, Pressure
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/1514402
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