Multiscale modeling of crowdion and vacancy defects in body-centered-cubic transition metals
Multiscale modeling of crowdion and vacancy defects in body-centered-cubic transition metals
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DOI：
10.1103/physrevb.76.054107
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发表时间：
2007-08-01
影响因子：
3.7
通讯作者：
Dudarev, S. L.
中科院分区：
文献类型：
--
作者：
Derlet, P. M.;Nguyen-Manh, D.;Dudarev, S. L.
我们研究了元素周期表中5B族（钒、铌和钽）和6B族（铬、钼和钨）的体心立方过渡金属中单个自间隙原子的结构和迁移率以及空位缺陷。密度泛函计算表明，在所有这些金属中，轴对称< 111 >的自间隙原子构型具有最低的形成能。在铬中，< 111 >自间隙构型与< 110 >自间隙构型之间的能量差非常小，使得这两种结构几乎简并。形成群集构型核心的原子的局域态密度表现出局域d带的系统加宽和反键峰的向上移动。利用电子结构计算提供的信息，我们推导出了钒、铌、钽、钼和钨的finnis - sinclair型原子间势族。利用这些势，我们研究了钨中自间隙原子缺陷的热激活迁移。我们利用描述缺陷和声子激励之间非线性弹性相互作用的多弦Frenkel-Kontorova模型的解析解来合理化模拟结果。我们发现晶格的离散性在缺陷迁移率中起着主导作用。我们还能够解释非阿伦尼乌斯扩散的起源，并表明在高温下，扩散系数作为绝对温度的函数呈线性变化。
We investigate the structure and mobility of single self-interstitial atom and vacancy defects in body-centered-cubic transition metals forming groups 5B (vanadium, niobium, and tantalum) and 6B (chromium, molybdenum, and tungsten) of the Periodic Table. Density-functional calculations show that in all these metals the axially symmetric < 111 > self-interstitial atom configuration has the lowest formation energy. In chromium, the difference between the energies of the < 111 > and the < 110 > self-interstitial configurations is very small, making the two structures almost degenerate. Local densities of states for the atoms forming the core of crowdion configurations exhibit systematic widening of the "local" d band and an upward shift of the antibonding peak. Using the information provided by electronic structure calculations, we derive a family of Finnis-Sinclair-type interatomic potentials for vanadium, niobium, tantalum, molybdenum, and tungsten. Using these potentials, we investigate the thermally activated migration of self-interstitial atom defects in tungsten. We rationalize the results of simulations using analytical solutions of the multistring Frenkel-Kontorova model describing nonlinear elastic interactions between a defect and phonon excitations. We find that the discreteness of the crystal lattice plays a dominant part in the picture of mobility of defects. We are also able to explain the origin of the non-Arrhenius diffusion of crowdions and to show that at elevated temperatures the diffusion coefficient varies linearly as a function of absolute temperature.