First-principles calculation on structure stability, thermodynamic and mechanical properties of Mg<sub>2</sub>Si intermetallics

Abstract

Lattice constants, thermodynamic parameter and elastic constant of Mg2Si intermetallics were investigated by means of first-principle calculations from CASTEP program based on density functional theory. Density, structural stability, elastic modulus, hardness and melting point of Mg2Si were deduced by theoretical formula and empirical formula. The calculated lattice constants, thermodynamic parameter and elastic constant are in good agreement with the experimental and other theoretical value, which proved that first-principles calculation has high credibility. The enthalpy of formation and the cohesive energy of Mg2Si are deduced by calculated thermodynamic parameter. Results show that the enthalpy of formation and the cohesive energy are both negative. It demonstrates that Mg2Si easier to form a stable compound with the strong alloying capability. Density ( ρ ), elastic modulus ( E ), shear modulus ( G ), bulk modulus ( B ), Poisson’s ratio ( ν ) and anisotropic ( A ) are derived. The calculated density, elastic constants of monocrystal Mg2Si are in good agreement with the experimental and other theoretical value. The results demonstrate that Mg2Si is provided with low density, high elastic modulus and poor plasticity and Mg2Si phases is brittle phases. Hardness and melting point of Mg2Si were forecasted by empirical formula. It demonstrates that Mg2Si have high hardness and high melting point.