Electronic, elastic and thermodynamic properties of LaMgRe4 (Re= Co, Ni, Cu): A first-principles study

Abstract

The magnesium-based alloys are excellent hydrogen storage materials due to outstanding physical and chemical properties. In recent years, ternary magnesium-based alloys have attracted extensive attention of scientists and researchers. In this work, the electronic, elastic and thermodynamic properties of the ternary metallic compounds LaMgRe4 (Re = Co, Ni, Cu) have been investigated in detail utilizing first-principles based density functional theory (DFT). The calculated results of formation enthalpy (ΔH) of LaMgCo4, LaMgNi4 and LaMgCu4 are −0.0641eV/atom, −0.3064 eV/atom and −0.1416eV/atom respectively, indicating that these three alloys can exist stably. The elastic constants (Cij) and phonon dispersion curves show that the three alloys conform to the mechanical and dynamic stability. In addition, the elastic modulus of polycrystals is obtained from the elastic constants of single crystals. The results of bulk modulus (B), shear modulus (G), Young's modulus (E), Poisson's ratio (ν), B/G and anisotropic coefficient (A) indicate that the ternary metallic compounds LaMgRe4 are anisotropic materials with ductility and plasticity. The thermodynamic properties such as enthalpy, free energy, entropy and heat capacity of the three alloys are obtained by phonon calculations for wide temperature range from 0 K to 1000 K, and further discussed in detail. Finally, the elastic constants of random solid solution alloys of La4Mg4Ni16-xCox (x = 0.4, 0.8, 1.6), La4Mg4Ni16-xCux (x = 2, 4, 8) and the adsorption of H2O molecule on LaMgNi4 (110) surface are also investigated.