2018 Volume 59 Issue 6 Pages 890-896
To investigate the stability of various Mg-based Laves phases, the formation enthalpy and phonon dispersion were obtained by first-principles calculation. The calculated formation enthalpy and phonon dispersion indicate that MgX2 (X = Al, Co, Ni, Cu, Zn) and Mg2X (X = Ca, Sr, Y, Ba, La) are stable both statically and dynamically. These results are consistent with the experimental results except for MgAl2 and Mg2La. These compounds are considered to be in a metastable state in each binary system. We also used the cluster expansion method to examine the possibility of adding a third element to MgZn2. Our theoretical investigations suggest attractive interaction between Zn and a third element such as Ag, Ca, and Zr in the MgZn2 lattice. However, Ca and Zr replace a small amount of Zn in MgZn2 owing to the instability of MgCa2 and MgZr2, in agreement with the experimental result. Furthermore, it is suggested that Zr becomes stable at the Mg site in the MgZn2 lattice owing to the stability of ZrZn2.