活性元素Ti和SiO2界面结合机制的第一性原理计算

First principle calculation of the binding mechanism between Ti and SiO2

关键词:  钛/二氧化硅|第一性原理|界面结合机制|分离功|电子行为

Key words:  Ti/SiO₂|first principle calculation|interface bonding mechanism|work of separation|electron behavior

摘要:

Ti元素是钎焊SiO_2f/SiO₂复合材料重要的活性元素，因此，使用第一性原理计算研究了Ti和SiO₂的界面结合机制. 分别建立了两种不同的终止面和化学计量比的界面，使用界面分离功、电子行为和界面能研究了界面原子间的结合. 结果表明，在O终止界面中，界面处Ti和O形成很强的离子-共价键，界面分离功最大可达到8.99 J/m². 在Si终止面界面中，Ti和Si形成共价-离子键，界面分离功为2.65 J/m². 在温度为1 173 K时，当Si的活度大于e⁻³⁵时，富Si界面的界面能更低，界面倾向于形成Ti-Si化合物. 当Si的活度小于e⁻³⁵时，富O界面在热力学上更加稳定，界面倾向于形成Ti-O化合物. SiO₂中的Si被Ti置换出后，Si扩散进入钎料，活度升高，与钎料中的Ti反应生成Ti-Si化合物，所以界面结构为SiO₂/Ti-O化合物/Ti-Si化合物/钎料.

Abstract:

Ti is an important active element to join SiO_2f/SiO₂ composite materials. Therefore, the bonding mechanism of Ti and SiO₂ was studied by using first principle calculation. Two kinds of interfaces with different termination and stoichiometric ratio were studied by the results of work of separation (W_sep), electron behavior and interface energy. It is found that in the O-terminated interface, Ti and O atoms form a strong ionic-covalent bonding, resulting in the largest W_sep of 8.99 J/m². In the Si-terminated interface, Ti and Si atoms form covalent-ionic bonding, and the W_sep is 2.65 J/m². At the temperature of 1 173 K, when the activity of Si is larger than e⁻³⁵, the interface of Si-terminated interface is more lower. The Ti-Si compounds are more favored at the interface. When the activity of Si is smaller than e⁻³⁵, the O-terminated interface is more stable in thermodynamics and the Ti-O compounds are more favored at the interface. After Si in SiO₂ in replaced by Ti, Si will diffuse into the solder and react with Ti in the solder to form Ti-Si compounds, so the interface struture is SiO₂/Ti-O compound/Ti-Si compound/solder.