Elastic and electronic properties of tI26-type Mg12RE (RE = Ce, Pr and Nd) phases

A detailed theoretical study of structural, elastic and electronic properties of tI26-type Mg12RE (RE = Ce, Pr and Nd) phases has been carried out by means of first-principles calculations based on density functional theory. The optimized lattice parameters at T = 0 K are in excellent agreement with the available experimental value at room temperature, and the obtained formation enthalpies show that with increasing atomic number of RE, the stability of Mg12RE alloys becomes lower. The elastic constants of tI26 Mg12RE are further calculated, then the bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν of polycrystalline aggregates are derived, and the relevant mechanical properties of Mg12RE alloys are also discussed. The elastic anisotropy of the three alloys is studied in detail using several methods, and the three-dimensional directional representation reveals the variation of Young's modulus along the crystallographic direction visually and completely. Finally, electronic density of states, charge density distribution and Bader charges are also calculated to reveal the underlying mechanism of structural stability and mechanical properties. (paper)