Kato Akihiko, Yagi Takeshi, Fukusako Naoto
FDK Corporation, 2281 Washizu, Kosai, Shizuoka, Japan.
J Phys Condens Matter. 2009 May 20;21(20):205801. doi: 10.1088/0953-8984/21/20/205801. Epub 2009 Apr 24.
We have studied intrinsic point defects in magnesium silicide, Mg(2)Si, by density-functional theory. Evaluating the formation energies of point defects, we show that n-type electric conductivity of Mg(2)Si originates from formations of positively charged Mg ions at interstitial sites, regardless of the chemical composition in crystal growth. Moreover, we have calculated the Born effective charge tensors and the valence charge density distribution. They show Mg(2)Si is an ionic crystal composed of Mg(2+) and Si(4-) which have very different ionic radii, 0.6 Å and 2.1 Å, respectively. We have concluded that the unfavorable antisite defect, Mg(Si), is due to the dissimilar ionic radii.
我们通过密度泛函理论研究了硅化镁（Mg₂Si）中的本征点缺陷。通过评估点缺陷的形成能，我们表明Mg₂Si的n型电导率源自间隙位置带正电的Mg离子的形成，与晶体生长中的化学成分无关。此外，我们计算了玻恩有效电荷张量和价电荷密度分布。结果表明，Mg₂Si是一种由Mg²⁺和Si⁴⁻组成的离子晶体，它们的离子半径分别为0.6 Å和2.1 Å，差异很大。我们得出结论，不利的反位缺陷Mg(Si)是由于离子半径不同所致。
