Al3V表面氧吸附的第一性原理研究

First-principles study on the adsorption of oxygen on Al3V surfaces

摘要:

采用基于密度泛函理论的第一性原理方法，计算了低指数Al3V表面的表面能，分析其稳定性；然后采用最稳定表面研究了Al3V表面的O吸附行为以及合金元素的影响。结果表明，终止于Al原子的(110)面是最稳定的表面。O原子倾向于吸附在(2×1)-(110)-Al表面桥位，且随着覆盖度增加，O吸附的稳定性增加。从DOS分析和O与表面各原子的间距可以推断，该表面在氧化的初始阶段发生Al的氧化和V的内氧化，氧化后有可能形成具有保护性的Al2O3膜。合金元素Ti和Cr均倾向于占据表面第2层V原子位，且都促进O原子在表面的吸附，但2者的作用机制不同，Ti与O相互作用较强，从而降低了Al与O的相互作用，在氧化过程中Ti与Al有可能同时氧化，从而形成Al和Ti的混合氧化物；Cr对于Al和O的相互作用有微弱的增强作用，使得O的吸附更加稳定，可能会促进Al的氧化，从而形成保护性的Al2O3。

关键词:第一性原理;Al₃V表面;氧吸附;

Abstract:

By use of first-principles calculations based on density-functional theory, the stability of low-index surfaces of Al3V intermetallic were analyzed, then the adsorption of oxygen on Al3V surface and the effects of alloying elements were studied with the most stable surface. The results show that Al-terminated (110) surface is the most stable. The adsorption of oxygen at brige sites of the surface are preferable, and the adsorption of oxygen are more and more stable as the coverage increases. It can be inferred from DOS analysis and the distance between O and other atoms that at the initial stages the oxidation of Al atoms and internal-oxidation of V atoms occurred, that means the protecting Al2O3 scale can be formed after oxidation. Ti and Cr atoms prefer to substitue V atoms in 2nd layer, the substitution of the atoms can both improve the adsorption stability of oxygen on the surface, while the mechanisms are different. The interactions between Ti and O atoms are strong, so the interactions between Al and O atoms are weakened after Ti substitution, that means Ti and Al can both be oxidized to form mixed oxides. On the other hand, the interactions between Al and O atoms are slightly enhanced after Cr substitution, so the oxidation of Al atoms are improved, that means the protective Al2O3 scale can be formed.

Key words:first-principles; Al₃V surfaces; oxygen adsorption