钒酸铋中的钼缺陷络合物
Molybdenum Defect Complexes in Bismuth Vanadate
摘要：
单斜钒酸铋（BiVO $_4$）是一种具有良好应用前景的$n$型半导体材料。几项研究表明，其光催化活性大大提高了高浓度的钼和钨掺杂剂。在目前的工作中，我们进行了\textit{ab initio}计算，以评估在BiVO $_4$中Mo相关对之间的最有利的相对位置。令人惊讶的是，我们验证了最低的能量配置为钼$_{\text{V}}$成对缺陷BiVO $_4$发生在最近的邻居网站，尽管较高的静电斥力和较大的应变的晶格。对于W掺杂的BiVO $_4$中的W $_{\text{V}}$缺陷对观察到类似的结果。我们表明，这种效果的起源在于一个有利的杂交的杂质的原子轨道之间，只有当它们是最接近彼此验证，从而克服了对形成能量的排斥成分的焓增益。因此，Mo和/或W掺杂的BiVO $_4$可能存在供体-供体缺陷复合物，这是可以应用于实验方法以改善这些金属氧化物的光催化活性的结果。
英文摘要：
Monoclinic bismuth vanadate (BiVO$_4$) is a promising $n$-type semiconductor for applications in sunlight-driven water splitting. Several studies have shown that its photocatalytic activity is greatly enhanced by high concentrations of Mo and W dopants. In the present work, we performed \textit{ab initio} calculations to assess the most favorable relative position between Mo-related pairs in BiVO$_4$. Surprisingly, we verify that the lowest energy configuration for Mo$_{\text{V}}$ pairwise defects in BiVO$_4$ occurs on nearest-neighbor sites, despite the higher electrostatic repulsion and larger strain on the crystal lattice. Similar results were observed for W$_{\text{V}}$ defect pairs in W-doped BiVO$_4$. We show that the origin of this effect lies in a favorable hybridization between the atomic orbitals of the impurities that is only verified when they are closest to each other, resulting in an enthalpy gain that overcomes the repulsive components of the pair formation energy. As a consequence, Mo and/or W doped BiVO$_4$ are likely to present donor-donor defect complexes, which is an outcome that can be applied in experimental approaches for improving the photocatalytic activity of these metal oxides.
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