Influence of the stereochemically active bismuth lone pair structure on ferroelectricity and photocalytic activity of Aurivillius phase Bi2WO6

Abstract

Ab initio electronic structure calculations are reported for the simplest (layered) Aurivillius compound, Bi 2 WO 6 , elucidating the role of the asymmetric Bi 6s lone-pair structure on the stability of the ferroelectric phase and the band structure. In contrast with the conventional view, where the nature of the para-to ferroelectric transition is explained by the formation of a short Bi-O bond to the perovskite layer, we show that the phase transition is accompanied by cooperative distortions of the asymmetric oxygen arrangements around the bismuth with the formation of particular short Bi-O bonds within the Bi 2 O 2 fluorite sheets. These changes are intimately connected to electronic properties, since while the high-temperature paraelectric phase possesses an indirect band gap, an unusual direct band gap is found at the zone center of the Brillouin zone for ferroelectric Bi 2 WO 6 .

First-principles study of the ferroelectric Aurivillius phase Bi2WO6

“…For the B2cb phase we notice that, while LDA underestimates the lattice constants, in this case, the GGA calculation of Mohn and Stolen [17] overestimates them clearly. The related energy, with respect to the I4/mmm phase, are reported in Table VIII.…”

Enhanced photocatalytic activities of Bi2WO6 by introducing Zn to replace Bi lattice sites: a first-principles study

“…In addition, the smaller ionic radii of Zn 2+ (0.70Å) than that of Bi 3+ (1.03Å) will lead to the distortion of the crystal structure. Mohn et al showed that the lone pair of bismuth is stereochemically active in Bi 2 WO 6 [37]. According to the revised lone pair (RLP) theory [38], the sterochemically active bismuth lone pair structure will be enhanced by distorting the crystal structure, which is meaningful from aspects of physics and applications.…”

Two‐Orbital Three‐Electron Stabilizing Interaction for Direct Co2+As3+ Bonds involving Square‐Planar CoO4 in BaCoAs2O5

“…The mixing of the empty p orbitals of the cation (e.g., 6s 2 6p 0 for Bi 3+ ) into these antibonding states, which is enhanced by an asymmetric distortion around the cation, forms the LP of the cation 1. 2 Systems with such a cation LP orbital cover a broad range of interesting materials, which include photocatalysts with optical transitions involving the LP states at the top of the valence bands (e.g., BiVO 4, 3 Bi 2 WO 6 ),4 multiferroics based on the pyramidal inversion of the cation with LP (e.g., perovskites BiMnO 3 , and BiFeO 3 )5 and low‐band‐gap transparent conducting materials with hole conduction, (e.g. good p ‐type mobilities in SnO and PbO2).…”