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.