莫来石型正交晶Bi 2 M 4 O 9（M = Al 3+，Ga 3+）的结构，电子和光学性质的第一性原理研究,Inorganic Chemistry

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莫来石型正交晶Bi ₂ M ₄ O ₉（M = Al ³⁺，Ga ³⁺）的结构，电子和光学性质的第一性原理研究
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2016-05-03 00:00:00 , DOI: 10.1021/acs.inorgchem.6b00330
Ehsan Zahedi ₁ , Bing Xiao ₂ , Mohadese Shayestefar ₃

Affiliation

运用密度泛函理论，研究了莫来石型斜方晶Bi ₂ M ₄ O ₉（M = Al ³⁺，Ga ³⁺）晶体的结构，电子能带结构，态密度，投影波函数和光学性质。广义梯度近似框架中的范德比尔特超伪拟势作为交换相关函数。实验和理论结果之间的令人满意的一致性表明所使用的方法和条件是合适的。四面体MO ₄环境中的M–O键相对于八面体MO ₆更强且更共价; 在这两个研究结构中，Bi-O键本质上几乎都是离子性的。Bi ₂ Al ₄ O ₉和Bi ₂ Ga ₄ O ₉的光催化活性由于在MO ₄，MO ₆和BiO ₆ E基团中O原子上的Mulliken电荷值不相等而得到增强。Bi ₂ Al ₄ O ₉和Bi ₂ Ga ₄ O ₉是带隙分别为2.71和2.86 eV的直接和间接带隙半导体。Bi ₂ Al ₄ O _9的较高光催化活性与Bi ₂ Ga ₄ O ₉相比，由导带最小值和价带最大值附近的光生载流子的较低有效质量可以推断出α的存在。在价带和导带中存在M和O轨道表明，MO ₄和MO ₆单元中的对称性断裂在分离电荷和增加光催化活性方面具有重要作用。从带边缘电位证实了Bi ₂ Al ₄ O ₉和Bi ₂ Ga ₄ O ₉对有机污染物的分解和水分解产生氢的光催化活性。

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

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.

更新日期：2016-05-03

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