First Principles Study of Structural Stability, Elastic Properties, and Electronic Structures of Y-Doped Mg2Si

The occupancy, structural stability, elastic properties, and electronic structure of Y-doped Mg2Si were calculated by the first principles method based on density functional theory. Calculation of the formation heats and mechanical stability show that Mg2Si, and Mg7Si4Y can be stable, while Mg8Si3Y and Mg8Si4Y cannot exist stably in the system. The heats of formation and cohesive energies calculations show that the structural stability and alloying ability of Mg7Si4Y is better than that of Mg2Si. The bulk modulus (B), shear modulus (G), Young's modulus (E), and Poisson's ratio (nu) show that Mg2Si is a brittle phase and Mg7Si4Y is a ductile phase. Doping with Y can improve the ductility of Mg2Si. The density of states, population analysis, and electron density difference show that the ionicity of Mg7Si4Y is stronger than that of Mg8Si4, and the Y-Si ionic bonds formed by Mg7Si4Y increase the structural stability. The band structure analysis shows that the Fermi level of Mg7Si4Y is in the conduction band, the electrons in the valence band can easily transition to the conduction band, and that the conductivity of Mg7Si4Y is stronger than Mg2Si.