Self-diffusion of Fe and Pt in L1-Ordered FePt: Molecular Dynamics simulation
Self-diffusion of Fe and Pt in L1-Ordered FePt: Molecular Dynamics simulation
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DOI：
10.1016/j.commatsci.2021.110337
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发表时间：
2021-05
影响因子：
3.3
通讯作者：
S. Konorev;R. Kozubski;M. Albrecht;I. Vladymyrskyi
中科院分区：
文献类型：
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作者：
S. Konorev;R. Kozubski;M. Albrecht;I. Vladymyrskyi
利用分子动力学（MD）模拟计算了1300 ~ 1600 K温度范围内Fe和Pt原子在化学有序L10-FePt相中空位介导的晶格扩散系数.由于L10有序FePt相的各向异性结构，考虑了Fe和Pt沿沿着和垂直于[0 0 1]晶向的扩散通量和由此产生的自扩散系数.鉴于在真实的FePt单晶中的非常低的空位浓度，通过将针对较高空位浓度估计的自扩散系数具体缩放到平衡空位浓度来近似模拟过程的稳态条件。这个过程涉及的空位形成能的计算，出现温度依赖性。该方法的有效性进行了彻底的测试，并对最终结果进行了分析，并与相关文献数据进行了比较。计算的Fe和Pt自扩散系数随温度的变化均表现为Arrhenius行为，但其值远低于文献报道的实验值。除了所施加的准经验势的不可避免的影响，差异可能源于这样一个事实，即虽然MD模拟解决了FePt的单晶缺陷完全与空位和反位，存在的快速扩散路径沿着线性和平面缺陷不能排除在真实的材料中。
Vacancy-mediated lattice diffusion coefficients of Fe and Pt atoms in the chemically orderedL10-FePt phase at temperatures between 1300 and 1600 K were evaluated by means of Molecular Dynamics (MD) simulations. Due to the anisotropic structure of theL10-ordered FePt phase, Fe and Pt diffusion fluxes and the resulting self-diffusion coefficients were considered along and perpendicular to the [0 0 1] crystallographic direction. In view of a very low vacancy concentration in real FePt single crystals, steady state conditions of the simulated process were approximated by specifically scaling the self-diffusion coefficients estimated for higher vacancy concentrations to the equilibrium vacancy concentration. This procedure involved the calculation of vacancy formation energies which appeared temperature dependent. The validity of this approach was thoroughly tested and the final results were analyzed and compared to the relevant literature data. The evaluated temperature dependent Fe and Pt self-diffusion coefficients showed Arrhenius behavior, however, their values were much lower than the reported experimental ones. Apart from the inevitable effect of the applied quasi-empirical potentials, the discrepancies might originate from the fact that while the MD simulations addressed a single crystal of FePt defected exclusively with vacancies and antisites, the existence of fast diffusion paths along linear and planar defects cannot be excluded in real materials.