First-Principles Study on Structural and Thermoelectric Properties of Al- and Sb-Doped Mg2Si
First-Principles Study on Structural and Thermoelectric Properties of Al- and Sb-Doped Mg2Si
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DOI：
10.1007/s11664-014-3508-4
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发表时间：
2015-06-01
影响因子：
2.1
通讯作者：
Hamada, Noriaki
中科院分区：
文献类型：
--
作者：
Hirayama, Naomi;Iida, Tsutomu;Hamada, Noriaki
本文用第一性原理计算理论研究了含Al或Sb原子为杂质的硅化镁（Mg2Si）的结构和热电性质。我们利用基于密度泛函理论的伪势方法，通过变胞松弛来优化结构性能。结果表明，杂质原子的加入会影响晶格常数，这主要是因为这些杂质的离子半径与基体成分Mg和Si的离子半径不同。然后，我们估计，在优化结构的基础上，利用形成能计算杂质原子的位置偏好。结果表明，在低掺杂水平（< 2 at.%）下，Al倾向于进入具有相当形成能的Si、Mg和间隙位；在较高的掺杂水平（< 4 at.%）下，它可以优先取代Mg位点。另一方面，Sb在任何杂质浓度下都表现出对Si位的强烈偏好。此外，我们利用全势线性化增强平面波方法和玻尔兹曼输运方程，得到了Al和sb掺杂Mg2Si的热电动势（塞贝克系数）与温度的关系。
We theoretically investigate the structural and thermoelectric properties of magnesium silicide (Mg2Si) incorporating Al or Sb atoms as impurities using first-principles calculations. We optimized the structural properties through variable-cell relaxation using a pseudopotential method based on density functional theory. The result indicates that the lattice constant can be affected by the insertion of impurity atoms into the system, mainly because the ionic radii of these impurities differ from those of the matrix constituents Mg and Si. We then estimate, on the basis of the optimized structures, the site preferences of the impurity atoms using a formation energy calculation. The result shows a nontrivial concentration-dependence of the site occupation, such that Al tends to go into the Si, Mg, and interstitial sites with comparable formation energies at low doping levels (< 2 at.%); it can start to substitute for the Mg sites preferentially at higher doping levels (< 4 at.%). Sb, on the other hand, shows a strong preference for the Si sites at all impurity concentrations. Furthermore, we obtain the temperature-dependence of the thermoelectromotive force (Seebeck coefficient) of the Al- and Sb-doped Mg2Si using the full-potential linearized augmented-plane-wave method and the Boltzmann transport equation.