Finite-temperature thermodynamic and vibrational properties of Al-Ni-Y compounds via first-principles calculations

The thermodynamic properties of ternary compounds of the Al-Ni-Y system were studied via density functional theory using the projector augmented-wave pseudopotential method, within the generalized gradient approximation. It was found that spin-polarization effects in all of the compounds are negligible. For three of the compounds, the ground state structures were determined for the first time by minimizing their total energies with respect to all the possible atomic arrangements consistent with their published space group and prototype structure. The calculated enthalpies of formation at 0 K show a very good agreement with the available experimental results at room temperature. The finite temperature thermodynamic properties of the compounds were calculated by considering the effects of both vibrational and electronic degrees of freedom. Lattice vibration effects were calculated using the supercell method within the harmonic and quasi-harmonic approximations. The thermal electronic contributions were determined through the one-dimensional integration of the electronic density of states.