Cuko Andi, Bromley Stefan T, Calatayud Monica
Departament de Ciència de Materials i Química Física, Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Barcelona, Spain.
CNRS, Laboratoire de Chimie Théorique, LCT, Sorbonne Université, Paris, France.
Front Chem. 2019 Feb 7;7:37. doi: 10.3389/fchem.2019.00037. eCollection 2019.
Oxygen vacancies are related to specific optical, conductivity and magnetic properties in macroscopic SiO and TiO compounds. As such, the ease with which oxygen vacancies form often determines the application potential of these materials in many technological fields. However, little is known about the role of oxygen vacancies in nanosized materials. In this work we compute the energies to create oxygen vacancies in highly stable nanoclusters of (TiO), (SiO), and mixed (TiSiO) for sizes between = 2 and = 24 units. Contrary to the results for bulk and surfaces, we predict that removing an oxygen atom from global minima silica clusters is energetically more favorable than from the respective titania species. This unexpected chemical behavior is clearly linked to the inherent presence of terminal unsaturated oxygens at these nanoscale systems. In order to fully characterize our findings, we provide an extensive set of descriptors (oxygen vacancy formation energy, electron localization, density of states, relaxation energy, and geometry) that can be used to compare our results with those for other compositions and sizes. Our results will help in the search of novel nanomaterials for technological and scientific applications such as heterogeneous catalysis, electronics, and cluster chemistry.
氧空位与宏观SiO和TiO化合物中的特定光学、导电性和磁性相关。因此，氧空位形成的难易程度通常决定了这些材料在许多技术领域的应用潜力。然而，关于氧空位在纳米材料中的作用却知之甚少。在这项工作中，我们计算了在尺寸介于2至24个单元之间的高度稳定的(TiO)、(SiO)和混合(TiSiO)纳米团簇中产生氧空位的能量。与体相和表面的结果相反，我们预测从全局最小的二氧化硅团簇中去除一个氧原子在能量上比从相应的二氧化钛物种中更有利。这种意外的化学行为显然与这些纳米级系统中末端不饱和氧的固有存在有关。为了充分表征我们的发现，我们提供了一组广泛的描述符（氧空位形成能、电子定位、态密度、弛豫能和几何结构），可用于将我们的结果与其他组成和尺寸的结果进行比较。我们的结果将有助于寻找用于技术和科学应用（如多相催化、电子学和团簇化学）的新型纳米材料。
