A direct method is used to calculate phonon dispersions of ${\mathrm{Al}}_3\mathrm{Li}$ based on the Hellmann-Feynman forces obtained from first-principles plane-wave pseudopotential calculations. The vibrational and thermodynamic properties of ${\mathrm{Al}}_3\mathrm{Li}$ are calculated by using the quasiharmonic approximation at finite temperature, in comparison with the calculations of ${\mathrm{Al}}_4$ in fcc structure to understand the alloying effect of Li. The calculated quantities, such as phonon dispersions, Grüneisen parameter, heat capacity, thermal expansion coefficient, and bulk modulus as a function of temperature, are discussed and compared with available experimental data.

• Received 10 November 1999

DOI:https://doi.org/10.1103/PhysRevB.61.14531