First-principles study of crystal structure prediction, electronic, thermodynamic and mechanical properties of Al-Li binary system

Abstract First-principles calculations based on density functional theory (DFT) have been used to search for the energetically stable crystal structures in the Al-Li binary system throughout all possible Al concentrations. Five ground state structures are found at Li5Al2, Li4Al2, Li3Al2, Li2Al2 and Li1Al15 compositions. The electronic, thermodynamic and mechanical properties of all these structures are systematically investigated. We analyze the formation energies, phonon spectra, and elastic tensor to confirm the energy, thermodynamic and elastic stabilities, respectively. The electronic band structures and corresponding density of states indicate the metallic nature of these structures. We also analyze the bulk modulus B, shear modulus G, Young’s modulus E, the Poisson’s ratio ν and B/G ratio as a function of the Li concentration in Al-Li binary system, and the spatial direction dependences of elastic moduli. The elastic wave velocities and Debye temperature generally increase, while the melting temperature monotonically decrease with the increasing Li concentration. The calculated results are in good agreement with the existing experimental and theoretical data. The comprehensive understanding of the material properties will be vital for practical applications of the Al-Li binary system.