Effects of doping atoms (Sb, Te, Sn, P and Bi) on the equilibrium shape of Mg2Si from first-principles calculations

Abstract

The surface energies of Mg₂Si (100) and (111) facets doped with modifying elements (Sb, Te, Sn, P and Bi) are calculated using first-principles methods, aimed at investigating the effects of the incorporation of modifying elements on the morphological evolution of Mg₂Si. Based on the results of surface energy, the equilibrium shape of pure Mg₂Si is predicted to be an octahedron surrounded by {111} planes. With the incorporation of Te, Sn, P and Bi, the ratio between the surface energies of the (100) and (111) planes (r) drops compared with that of pure Mg₂Si, promoting the extension of the (100) facets and the contraction of the (111) facets on Mg₂Si grains. Accordingly, the trend in morphological evolution for Mg₂Si is from the initial octahedron composed of {111} planes to a truncated octahedron surrounded by {111} and {100} planes. The results also show that Te and P are more effective in promoting the appearance frequency of (100) facets on the Mg₂Si crystal and can be used as candidate modifiers to realize the artificial manipulation of the morphology of Mg₂Si into a truncated octahedron. The findings here provide new insights for understanding the morphological evolution of Mg₂Si induced by the incorporation of modifying elements, which contributes to guiding the development of new high-temperature-resistant light alloys.