Mechanical, electronic and thermodynamic properties of C14-type AMg₂ (A = Ca, Sr and Ba) compounds from first principles calculations

Using first principles total energy calculations within the generalized gradient approximation (GGA), we have investigated the mechanical and thermodynamics properties of C14-type Laves phases AMg₂ (A = Ca, Sr and Ba). Our results of equilibrium lattice parameters and formation enthalpy agree closely with previous experimental results. In particular we have discussed the thermodynamic stabilities and mechanical anisotropies of these phase structures. The polycrystalline elastic moduli have been deduced by Voigt-Reuss-Hill arithmetic approximation. Subsequently, the ductility and brittleness are characterized with the estimation from Pugh's rule (B/G) and Poisson's ratio. Additionally, the Debye temperature is calculated from the average elastic wave velocity obtained from bulk and shear moduli. The calculations of density of states and charge density difference are performed to reveal the underlying mechanism of electronic structure. Finally, variations of thermodynamic properties with temperature are predicted by calculating phonon frequencies combined within the quasi-harmonic approximation.