First-principles phase stability, magnetic properties and solubility in aluminum–rare-earth (Al–RE) alloys and compounds

First-principles density-functional calculations are used to study the phase stability, magnetic properties and solubilities in aluminum–rare-earth (Al–RE) alloys and compounds. The results are compared with those from potentials with f-electrons treated as valence/core electrons to calculate the phase stability of different Al–RE compounds. Using a small set of test structures, it is found that calculations with potentials with f-electrons in the valence band predict correctly all the known stable phases of Al–RE compounds. It is found that the contribution of magnetism in the compounds is crucial for predicting the correct ground-state Al3RE structures. The calculated magnetic moments are in excellent agreement with experimental values. The RE solubilities in Al are calculated, including both static total energy contributions as well as the free energies associated with atomic vibrations. The vibrational entropy serves to increase significantly the solubilities of RE elements in Al. The calculated solvus curves are in good agreement with the available experimentally measured values.

► The phase stability, magnetic property and solubility of aluminum rare-earth compounds are systematically studied by first-principles calculations.
► Magnetic contributions of the RE elements and compounds have a significant impact on the formation energy of ordered Al3RE compounds, and are responsible for the stability of the observed DO19 phases for the early Al3RE compounds.
► Standard potentials with f-electrons treated as valence band electron correctly predict all the stable phases of Al-RE compounds and frozen potentials are also in good agreements with experiments except one compound, Al3Yb.cP4.
► The vibrational entropy plays an important role in the solubility of RE in Al. The calculated solubility of RE decreases as the RE atomic number increases.
► The calculated solvus curves of Er and Yb are in very good agreement with experimental values.