Diffusion of tellurium at nickel grain boundaries: a first-principles study
Diffusion of tellurium at nickel grain boundaries: a first-principles study
复制标题
镍晶界处碲的扩散：第一性原理研究
作者：
Wang C. Y.;Han H.;Wickramaratne D.;Zhang W.;Wang H.;Ye X. X.;Guo Y. L.;Shao K.;Huai P.
Te在镍晶界中的行为对于镍合金在熔盐堆中的应用具有重要意义。研究了碲在镍的体相、表面相和四种晶界上的原子结构、稳定性、分凝行为和扩散势垒。我们的第一性原理计算表明Te的分凝在δ = 5（021）GB时最有利，在δ = 3（111）GB时最弱。Te的扩散势垒依次增大：11（11），12（221），13（111），14（021）。计算的Te在η = 11（11）上的扩散势垒比体中低0.35 eV，表明Te沿着该GB快速扩散。我们还考虑了应变对扩散的影响，发现它对不同的GB类型很敏感。当拉伸应变达到4%时，Te的扩散势垒分别降低了0.51 eV和0.15 eV（ε = 5（021）和ε = 11（11））。相比之下，对于λ = 3（111），这种影响可以忽略不计。
The knowledge of the behavior of Te in nickel grain boundaries (GB) is of significant importance for the application of nickel alloys in molten salt reactors. The atomic structures, stabilities, segregation behaviors and diffusion barriers of Te are studied for the bulk, surfaces and four kinds of GBs of nickel. Our first-principles calculations indicate the segregation of Te is most favorable at Σ = 5 (021) GB and the weakest at Σ = 3 (111) GB. The diffusion barriers of Te increase in sequence: Σ = 11 (11), Σ = 9 (221), Σ = 3 (111) and Σ = 5 (021). The calculated diffusion barrier of Te on Σ = 11 (11) is 0.35 eV lower than in the bulk, indicating a fast diffusion of Te along this GB. We also consider the effect of strain on the diffusion and find it to be sensitive to the different GB types. When the tensile strain is up to 4%, the diffusion barriers of Te are lowered by 0.51 eV and 0.15 eV for Σ = 5 (021) and Σ = 11 (11), respectively. In contrast, this effect for Σ = 3 (111) is negligible.