Interstitials in FeCr alloys studied by density functional theory
Interstitials in FeCr alloys studied by density functional theory
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DOI：
10.1103/physrevb.76.214110
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发表时间：
2007-12
影响因子：
3.7
通讯作者：
T. Klaver;P. Olsson;M. Finnis
中科院分区：
文献类型：
--
作者：
T. Klaver;P. Olsson;M. Finnis
密度泛函理论计算已被用于研究FeCr合金的松弛间隙结构。测定了69个间隙结构的离子基态和电子基态。在合金中放置了高达14 at的间隙。铬原子要么是单原子分散的，要么是聚集在一个由4x4x4个立方体组成的周期性重复的超级单体中。在超细胞内，间隙与Cr原子之间的距离是不同的。结果表明，距离间隙第三近邻的Cr原子仍能与间隙产生高达0.9 eV的相互作用。Cr-Cr相互作用的多体性质导致cr -间隙相互作用具有强烈的浓度依赖性。无缺陷合金中Cr-Cr相互作用也依赖于总Cr浓度。合金中Cr-Cr的有效斥力弱于纯铁环境。除了Cr浓度外，Cr-间隙的相互作用还取决于距离间隙第三近邻的Cr原子的色散水平。不同取向哑铃型间隙的形成能差与Cr浓度无关。我们发现Cr原子对间隙的长程影响不是由于间隙应变场突出到超胞的富Cr部分。发现费米能级和能带不是决定形成能的唯一控制参数。讨论了经验势的构造含义。
Density functional theory calculations have been used to study relaxed interstitial configurations in FeCr alloys. The ionic and electronic ground states of 69 interstitial structures have been determined. Interstitials were placed in alloys with up to 14 at. % Cr. Cr atoms were either monatomically dispersed or clustered together within a periodically repeated supercell consisting of 4x4x4 cubes of bcc unit cells. The distance between the interstitials and Cr atoms was varied within the supercells. It is shown that Cr atoms beyond third-nearest-neighbor distance from the interstitial can still have an interaction with it of up to 0.9 eV. The multibody nature of the Cr-Cr interactions causes the Cr-interstitial interaction to be strongly concentration dependent. The Cr-Cr interaction in defect-free alloys is also dependent on the overall Cr concentration. The effective Cr-Cr repulsion is weaker in alloys than in an environment of pure Fe. Apart from the Cr concentration, the Cr-interstitial interaction also depends on the dispersion level of Cr atoms beyond third-nearest-neighbor distance from the interstitial. The formation energy differences between dumbbell interstitials with different orientations are independent of the Cr concentration. We show that the long-range influence of Cr atoms on the interstitial is not due to the interstitial strain field protruding into Cr-rich parts of the supercells. The Fermi-level and band energies were found not to be the sole governing parameter in determining the formation energies. Implications for the construction of empirical potentials are discussed.