Studied On Mechanical Properties Of Anatase TiO₂ Based On First-principles

In recent decades, material science has become the focus of chemistry and chemical engineering, environmental protection and biotechnology and so on. TiO2 as a kind of metallic oxides, has a wide range of applications in electronics, dyes and chemicals. Especially in catalysis, TiO2 is a very common photo-catalyst and heterogeneous catalyst, it has occupied a pivotal position in the industrial catalyst. The production technology of TiO2 is very mature, we can invest the quality TiO2 nano-materials directly. Many researchers hope to understand the nature of oxide surfaces from TiO2, because it is appropriate for many experiments and analysis methods. Therefore, Ti O2 has been favored by many experimental and theoretical workers.There are many studies of TiO2 in electro-optical properties, but a few reports of anatase TiO2 in mechanics. In addition, TiO2 will produce a number of defects due to the different sputtering and annealing temperature in the process of preparation, and these defects have a tremendous impact in physical, chemical and optical properties of TiO2. Therefore, we optimized the structure of anatase TiO2 by CASTEP calculating software and the Debye model, compare optimized results with the experimental numerical that show the reliable of this method. The relationship of bulk modulus, specific heat and thermal expansion coefficient of Anatase TiO2 with temperature and pressure are calculated. We find the bulk modulus of TiO2 decreases as the temperature increases; and when the temperature is constant, the bulk modulus growth rapidly as the pressure increases. The variation curves of heat capacity and thermal expansion coefficient with temperature and pressure are the same. When the temperature is low, which increase rapidly with the increase of temperature. When the temperature is high enough, the effect of temperature on heat capacity and thermal expansion coefficient are small. This can help us have a better understanding of the impact with temperature and pressure to the properties of anatase TiO2, to achieve the guiding for the experiment.Secondly, the anatase TiO2 structure with intrinsic defects were optimized by MS. The geometrical optimization results show that the vacancy and interstitial defect have an effect on other atoms of structure, especially the atoms around the defects. The elastic properties of perfect anatase TiO2 and TiO2 with intrinsic defects are calculated. And we analyzed the effect of intrinsic defects on mechanical properties of anatase TiO2. These bulk modulus and shear modulus are calculated and analyzed which combined with the three kinds of approximation theory. These theoretical data have a certain guiding significance to study the intrinsic defects of anatase TiO2.