Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, People's Republic of China.
J Phys Condens Matter. 2013 Oct 30;25(43):435402. doi: 10.1088/0953-8984/25/43/435402. Epub 2013 Oct 4.
We show that any impurity will slow the diffusion of oxygen in Nb. Using a first-principles plane-wave pseudopotential method and the supercell model, we calculated the interaction energies between substitutional atoms (SA) (X = Ti, V, Ta, Zr, and Hf) and interstitial oxygen in a Nb matrix. All impurities act as traps for oxygen: undersized SA (Ti and V) have strongest binding at the nearest octahedral interstice, while for oversized SA (Zr and Hf), the strongest trapping site is the second-nearest octahedral interstice. We evaluated the diffusion coefficients of O in the Nb-X alloys using kinetic Monte Carlo (KMC) modeling based in the transition state theory, using our calculated oxygen migration energies. From this, the effective (average) X-O interaction energies were extracted using the Oriani model (Oriani 1970 Acta Metall. 18 147-57). The effective X-O interaction energies are close to the strongest interaction energies between X and O obtained from the direct supercell calculations. The phenomenological effective diffusion barrier obtained from the KMC modeling is close to the energy difference between the most stable configuration and the highest saddle point along the diffusion path. Both results demonstrate that the weaker trapping site has negligible influence on the diffusion of O.
我们证明任何杂质都会减缓氧气在铌中的扩散。使用第一性原理平面波赝势方法和超胞模型，我们计算了替代原子（SA）（X=Ti、V、Ta、Zr 和 Hf）与铌基体中间隙氧之间的相互作用能。所有杂质都对氧起陷阱作用：较小的 SA（Ti 和 V）在最近的八面体间隙处具有最强的结合能，而对于较大的 SA（Zr 和 Hf），最强的捕获位置是第二近的八面体间隙。我们使用基于过渡态理论的动力学蒙特卡罗（KMC）模型来评估 O 在 Nb-X 合金中的扩散系数，使用我们计算出的氧迁移能。由此，使用 Oriani 模型（Oriani 1970 Acta Metall. 18 147-57）从实验上提取了有效（平均）X-O 相互作用能。有效 X-O 相互作用能接近于直接超胞计算中 X 和 O 之间最强相互作用能。从 KMC 建模中获得的唯象有效扩散势垒接近于沿扩散路径最稳定构型和最高鞍点之间的能量差。这两个结果都表明，较弱的捕获位置对 O 的扩散几乎没有影响。
