Trapping of interstitial defects: filling the gap between the experimental measurements and DFT calculations
Trapping of interstitial defects: filling the gap between the experimental measurements and DFT calculations
复制标题
DOI：
10.1088/0953-8984/25/43/435402
复制
发表时间：
2013-10
期刊：
影响因子：
--
通讯作者：
Linggang Zhu;Hao Wang;Q. Hu;G. Ackland;Rui Yang
中科院分区：
文献类型：
--
作者：
Linggang Zhu;Hao Wang;Q. Hu;G. Ackland;Rui Yang
我们发现，任何杂质都会减缓氧在Nb中的扩散。采用第一原理平面波赝势方法和超晶胞模型，计算了Nb基质中替代原子(SA)(X=Ti、V、Ta、Zr和Hf)与间隙氧的相互作用能。所有杂质都是氧的陷阱：尺寸较小的SA(Ti和V)在最近的八面体空隙上有最强的结合，而过大的SA(Zr和Hf)，最强的陷阱位置是次近的八面体空隙。利用我们计算的氧迁移能，用基于过渡态理论的动力学蒙特卡罗(KMC)模型计算了O在Nb-X合金中的扩散系数。在此基础上，利用Oriani模型(Oriani 1970年金属学报)提取了有效的(平均)X-O相互作用能。18147-57)。有效的X-O相互作用能接近直接超胞计算得到的X和O之间的最强相互作用能。由KMC模型得到的唯象有效扩散势垒接近扩散路径上最稳定构型与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。
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.