A 2x2x2 supercell of the 12-atom cubic structure (96 atoms total) of Mg 2 Si was generated to perform defect calculations. Ionic relaxations were performed with a force convergence criterion of 0.02 eV/Å and a Γ-centered 49 k-point mesh density of 2x2x2 was used for all point defect calculations. A static calculation using the tetrahedron method with Blöchl corrections with an increased k-point mesh density of 3x3x3 was performed on the relaxed structures to produce accurate total energies and density of states.