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

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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 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 correctly predict 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 Al 3RE 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.