Electronic structure of MoO2. DFT periodic and cluster model studies
Electronic structure of MoO2. DFT periodic and cluster model studies
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DOI：
10.1016/j.apcata.2010.07.041
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发表时间：
2011-01
影响因子：
5.5
通讯作者：
R. Tokarz-Sobieraj;R. Grybos;M. Witko
中科院分区：
文献类型：
--
作者：
R. Tokarz-Sobieraj;R. Grybos;M. Witko
讨论了MoO 2体相和（011）面的电子性质。发现费米能级位于d钼轨道主导的能带内，反映了系统的金属性。对（011）MoO 2表面的研究表明，MoO 2表面保留了体相的金属特征。根据用于模拟表面的平板的厚度（1层或2层），电子结构和性质发生变化。在2层平板中，接近费米能级的能带来源于规则的六重配位Mo（6）中心以及由于表面形成而产生的五重配位Mo（5）中心。在单层板中，费米能级正下方的峰由六重配位Mo（6）的表面中心以及有效地四重配位Mo（4）的中心主导。这对反应性具有深远的影响，如通过H2吸附的探针反应所测试的，H2吸附不与由2层平板所描述的表面相互作用，但在1层平板上发生解离。Mo-Mo对具有近似单一特征的键，其特征为块状结构，也存在于表面上，在1层和2层板上。（011）MoO 2表面的局部性质与其它过渡金属氧化物非常相似。金属-氧键具有离子键和共价键的混合性质，氧的亲核性随着相应氧原子配位数的增加而增加。
Electronic properties of MoO2bulk and (011) surface are discussed. It is found that Fermi level is located within the band dominated by d molybdenum orbitals, thereby reflecting the metallic character of the system. Results for (011)MoO2surface indicate that the surface retains the metallic character of the bulk. Depending on the thickness of the slab used to model the surface (1-layer or 2-layers) the electronic structure and properties change. In the 2-layer slab, bands close to the Fermi level originate both from regular six-fold coordinated Mo(6) centers as well as from five-fold coordinated Mo(5) centers occurring due to surface formation. In the 1-layer slab, peaks right below the Fermi level are dominated by the surface centers that are six-fold coordinated Mo(6) but also centers which are effectively four-fold coordinated Mo(4). This has a profound effect on the reactivity as was tested by a probe reaction of H2adsorption, which did not interact with the surface described by the 2-layer slab, but underwent dissociation on the 1-layer slab. The Mo–Mo pairs with bonds of approximately single character, characteristic for the bulk structure, are also present on the surface, both on 1-layer and 2-layer slabs. The local properties of (011)MoO2surface are very similar to other transition metal oxides. Metal–oxygen bonds are of a mixed ionic and covalent nature and the nucleophilicity of oxygen increases with the increase of coordination numbers of the corresponding oxygen atoms.