LAUSR

Abstract Nine possible native point defects in ternary C14 Laves phase Mg 2 Cu 3 Si are investigated from ab initio calculation based on density function theory. The two-dimensional phase diagram of chemical potentials is determined, and then defect formation energy is calculated. The energetic results show that Cu Si and Cu Mg are more favorable over a broad range of chemical potentials. The formation enthalpies for defective Mg 2 Cu 3 Si also demonstrate the same stability. Local distortions around point defects increase from Si Cu to Si Mg , showing that the polyhedral symmetry and coordination number for constituent atoms will affect the structure of defects. The electronic structure shows the strong (Cu, Si)–Si covalent bonding, also indicates that the Cu Mg is favorable because the weak Mg-Cu bonding is replaced by the strong Cu–Cu bonding, whereas Mg Cu and Mg Si are unfavorable because the strong Cu–Si bonding is replaced by the weak Mg–(Cu, Si) bonding.