| Summary: | Being a positive candidate reinforcement material for laminar composites, the Mg<sub>2</sub>X (X = Si, Ge, Sn) based intermetallics have attracted much attention. The elastic properties, anisotropy, and electronic properties of intermetallic compounds with Bi-doped Mg<sub>2</sub>X (X = Si, Ge, Sn) are calculated by the first principles method. Results show that the lattice parameters of Mg<sub>2</sub>X are smaller than those of Bi-doped Mg<sub>2</sub>X. The element Bi preferentially occupies the position of the X (X = Si, Ge, Sn) atom than other positions. Mg<sub>2</sub>X (X = Si, Ge, Sn), Mg<sub>63</sub>X<sub>32</sub>Bi, Mg<sub>64</sub>X<sub>31</sub>Bi, Mg<sub>64</sub>Ge<sub>32</sub>Bi, and Mg<sub>64</sub>Sn<sub>32</sub>Bi are mechanically stable, while Mg<sub>64</sub>Si<sub>32</sub>Bi indicates that it cannot exist stably. The doping of alloying element Bi reduces the shear deformation resistance of the Mg<sub>2</sub>X (X = Si, Ge, Sn) alloy. The pure and Bi-doped Mg<sub>2</sub>X (X = Si, Ge, Sn) exhibits elastic and anisotropic characteristics. The contribution of the Bi orbitals of Mg<sub>63</sub>X<sub>32</sub>Bi, Mg<sub>64</sub>X<sub>31</sub>Bi, and Mg<sub>63</sub>X<sub>32</sub>Bi are different, resulting in different hybridization effects in three types of Bi-doped Mg<sub>2</sub>X.
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