Ab initio total energy calculations, based on the exact muffin-tin orbital (EMTO) theory, are used to determine the elastic properties of ${\mathrm{Al}}_{1-x}{\mathrm{Li}}_x$ random alloys $(x⩽0.20)$ in the face-centered-cubic crystallographic phase. The compositional disorder is treated within the framework of the single-site coherent potential approximation (CPA). The effect of the local lattice relaxation on the elastic constants is estimated using a supercell technique. We study the effect of the single-site approximation by comparing the theoretical ground-state properties calculated using different corrections to the Madelung energy. We find that the calculated equilibrium volumes and alloy formation energies strongly depend on the approximations employed in the Poisson equation, in accordance with former observations. At the same time, the experimental trends of the elastic moduli of disordered $\mathrm{Al}‐\mathrm{Li}$ alloys are well reproduced by the EMTO-CPA method. Using these theoretical results we show that the nonlinear effect of Li addition on the elastic constants originates from the detailed band structure of Al near the Fermi level.

• Received 26 April 2004

DOI:https://doi.org/10.1103/PhysRevB.71.014201