Influence of vacancy on the elastic, thermodynamic and electronic properties of LaMgNi4 alloys from first-principles calculations

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In this work, the structural stability, mechanical, electronic, and thermodynamic characteristics of LaMgNi4 alloys with different vacancies are discussed in detail. The calculated results of formation enthalpy (ΔH) of LaMgNi4 alloys with Mg-Va, Ni-Va2, La-Va1 and La-Va2 vacancies are −0.294eV/atom, −0.273eV/atom, −0.241eV/atom and −0.241eV/atom, respectively, and the results of phonon dispersion curves show that these vacancy models do not exhibit imaginary frequency in any high symmetry direction, which indicates that these models have stable structure. In addition, different vacancies have different effects on the mechanical properties of LaMgNi4 alloys. For example, the existence of Mg-Va, La-Va1, and La-Va2 vacancies enhances the mechanical properties of LaMgNi4 alloys, while the existence of Ni-Va2 vacancy weakens its mechanical properties. From the perspective of electronic structure, the change of mechanical properties of LaMgNi4 alloys is probably caused by the change of electronic state density at the Fermi level due to the existence of different vacancies. The thermodynamic properties such as the specific heat (Cv) and Debye temperature (ΘD) of the LaMgNi4 alloys with different vacancies are calculated by phonon calculations for wide temperature range from 0 K to 1000 K, and further discussed in detail. Finally, the adsorption of O atom on LaMgNi4 (110) surface and the elastic constants and the elastic modulus of random solid solution alloys of La4Mg4Ni14Cu2 are also investigated.