Electronic structures, elastic properties and debye temperature of the intermetallics in Mg-Zn-RE (RE=Ce, La)-Zr alloy: A first-principles calculation

The electronic, structural, elastic properties, and Debye temperature of Mg12Ce, Mg12La, CeMgZn2, and LaMgZn2 phases in Mg-Zn-RE (RE=Ce, La)-Zr Alloy are systematically calculated by first-principles method based on density functional theory (DFT). According to the calculated cohesive energies and formation enthalpies, LaMgZn2 exhibits the greatest structural stability while CeMgZn2 is easier to form than the other three phases under the same conditions. Analysis on the electronic structures reveals that CeMgZn2 and LaMgZn2 have metallic conductivity, and covalent and ionic bonds co-exist in Mg12Ce and Mg12La phases. Calculation on elastic properties shows that four phases are mechanically stable. Moreover, CeMgZn2 exhibits the highest stiffness and greatest resistance to deformation, while LaMgZn2 has the best plasticity. Calculation results of the elastic anisotropy indicate that both Mg12Ce and Mg12La exhibit anisotropy in AU, AB, AG, and E, while CeMgZn2 and LaMgZn2 show isotropic in AB and anisotropy in AU, AG, and E. A analysis of Debye temperature shows that Mg12La has the highest thermal stability among four phases. The above theoretical calculation helps to reveal the strengthening mechanism of Ce and La elements and design high strength magnesium alloys.