Defect and phase stability of solid solutions of Mg{sub 2}X with an antifluorite structure: An ab initio study
- Institut de Chimie Moleculaire et des Materiaux I.C.G., UMR-CNRS 5253, Universite Montpellier II, Place E. Bataillon, 34095 Montpellier Cedex 5 (France)
- Science et Ingenierie des Materiaux et Procedes, Grenoble INP, UJF, CNRS, 38402 Saint Martin d'Heres Cedex (France)
First principles calculations are done for Mg{sub 2}X (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 Mg{sub 2}Si-Mg{sub 2}Sn. This agrees with the most recent experiments and phase diagram assessments. Calculated electronic properties of Mg{sub 2}Si{sub 1-x}Sn{sub 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 Mg{sub 2}Si can be attributed to the presence of magnesium atoms in interstitial positions. In Mg{sub 2}Ge and Mg{sub 2}Sn, since other defects are stable, they can be also of p-type. - Graphical abstract: Evidence of a miscibility gap from the plot of the formation energy vs x{sub Si} (silicon content) for the solid solutions Mg{sub 2}Si-Mg{sub 2}Sn. Highlights: Black-Right-Pointing-Pointer First-principles study of the stability of Mg{sub 2}Si-Mg{sub 2}X alloys (X=Ge or Sn) and their defects. Black-Right-Pointing-Pointer Mg{sub 2}Si-Mg{sub 2}Ge alloys form a complete series of solid solutions. Black-Right-Pointing-Pointer Miscibility gap is found in Mg{sub 2}Si-Mg{sub 2}Sn alloys. Black-Right-Pointing-Pointer Interstitial defects are more stable in Mg{sub 2}Si and induce n-doping.
- OSTI ID:
- 22149813
- Journal Information:
- Journal of Solid State Chemistry, Vol. 193; Other Information: Copyright (c) 2012 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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