The cohesive and electronic properties and the structural stability of ${\mathrm{Al}}_3$Li in its fcc-based L$1_2$ and bcc-based D$0_3$ structures are investigated with use of the first-principles all-electron full-potential linear augmented-plane-wave (FLAPW) method. Particular care was taken to ensure convergence of the total energy as a function of the inherent numerical parameters in order to obtain high precision. To further understand the calculated stability, the electronic structure of some superstructures (notably ${\mathrm{Al}}_7$Li and ${\mathrm{Al}}_5$${\mathrm{Li}}_3$) was also determined. The equilibrium properties of the metastable L$1_2$ structure are in good agreement with experiment. A simple picture emerged which emphasizes the importance of the anisotropic bonding between the Al atoms with the Li basically donating its valence electron to strengthen the Al bonds. The bulk moduli were found to decrease with increasing Li content; by contrast, the calculated Young’s modulus of the L$1_2$ phase is high (1.20 Mbar) compared to the bulk modulus (0.72 Mbar). Both results are in keeping with the picture of anisotropic Al-Al bonding.

• Received 28 December 1989

DOI:https://doi.org/10.1103/PhysRevB.41.12432