Mechanical and dynamical properties of Co3Al and Co3Ta alloys in L1(2) phase

Abstract

The structural, elastic, electronic and vibrational properties of Co3Al and Co3Ta alloys with density functional theory have been investigated. The lattice constants, bulk modulus and its pressure derivative are evaluated and compared with the available data. The numerical first principles calculations of the elastic constants were used to calculate C-11, C-12 and C-44 for Co3Al and Co3Ta alloys. The electronic band structure, electronic total and partial densities of states, and total magnetic moment of the Co3Al and Co3Ta alloys are computed and analyzed in comparison with the existing findings. From the electronic calculations made for both alloys, it was found that the alloys were metallic in nature. Phonon-dispersion curves and their corresponding total and projected densities of states have been obtained for the first time using a linear-response in the framework of the density functional perturbation theory. The frequencies of the optical phonon modes of both alloys are calculated and found to be 4.46, 6.095 and 10.35 THz for Co3Al, 4.83, 6.11 and 6.86 THz for Co3Ta. Finally, specific heat capacity at a constant volume versus temperature CV of Co3Al and Co3Ta alloys is calculated and discussed using the quasi harmonic approximation.