Stabilization Effect of Surface Impurities on the Structure of Ultrasmall ZrO2 Nanoparticles: An Ab-Initio Study

详细信息    查看全文

• 作者：Roberto Grena ; Olivier Masson ; Laura Portal ; Fabien R茅mondi猫re ; Abid Berghout ; Jenny Jouin ; Philippe Thomas
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：July 9, 2015
• 年：2015
• 卷：119
• 期：27
• 页码：15618-15626
• 全文大小：469K
• ISSN：1932-7455

文摘

Real nanoparticles can hardly be considered as isolated objects in vacuum with pure stoichiometric chemical composition. It can be expected that some surface stabilizing mechanisms may occur in real systems, and they could induce more or less pronounced effects on the structure of nanoparticles. In this work, we analyzed the stabilizing effect of surface impurities on the structure of ultrasmall ZrO₂ nanoparticles using ab initio simulation methods. The study was performed on ZrO₂ cluster models, with a diameter around 1.25 nm, using the Car鈥揚arrinello molecular dynamics method combined with standard structural optimization methods. After the study of the naked cluster, the stabilizing effect was investigated by adding chemisorbed water molecules at the particle surface, with a covering degree ranging from 15% to 100%. The results clearly indicated that energy minimizations leaded invariably to highly disordered structures in the case of naked nanoparticles. The structure of the models got more ordered only with increasing water coverage. The comparison, via the pair distribution functions (PDF), to the experimental data obtained from a sample of nanoparticles of comparable size showed a good agreement for a high (but not total) water coverage, indicating that a surface stabilizing effect is a sound hypothesis to explain the experimental results. Surface stabilizing effects play a crucial role in the case of ZrO₂, in contrast with recent calculations performed on other chemical systems (CeO₂ or TiO₂, for example); thus, for ZrO₂ a stabilizing mechanism, such as the one proposed in this paper, must be inevitably included in the model, and this fact markedly complicates the problem of solving the ZrO₂ nanocrystal structure.