Defect and phase stability of solid solutions of Mg₂X with an antifluorite structure: An ab initio study

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• 作者：Romain Viennois ; Philippe Jund ; Catherine Colinet ; Jean-Claude T¨¦denac
• 关键词：Silicides ; ab-initio ; Stability ; Defects ; Thermoelectrics
• 刊名：Journal of Solid State Chemistry
• 出版年：2012
• 出版时间：September, 2012
• 年：2012
• 卷：193
• 期：Complete
• 页码：133-136
• 全文大小：248 K

文摘

First principles calculations are done for Mg₂X (X=Si, Ge or Sn) antifluorite compounds and their solid solutions in order to investigate their pseudo-binary phase diagram. The formation energies of the end-member compounds agree qualitatively with the experiments. For X=Si and Ge, there is a complete solubility, but we observe a miscibility gap in the pseudo-binary phase diagram Mg₂Si-Mg₂Sn. This agrees with the most recent experiments and phase diagram assessments. Calculated electronic properties of Mg₂Si_1?xSn_x alloys qualitatively agree with experiments and in particular the energy bandgap decreases when Si is substituted by Sn. Supercell calculations are also done in order to determine the most stable defects and the doping induced by these defects in the three end-member compounds. We find that the intrinsic n-doping in pure Mg₂Si can be attributed to the presence of magnesium atoms in interstitial positions. In Mg₂Ge and Mg₂Sn, since other defects are stable, they can be also of p-type.