Formation energies of θ-Al2Cu phase and precursor Al-Cu compounds: Importance of on-site Coulomb repulsion

Abstract

We investigated the relative stability and structural properties of Al-Cu intermetallic compounds using the density-functional theory (DFT) with different approximations. We reveal the importance of the on-site Coulomb repulsion of Cu 3d electrons on the energetics and structural properties of Al-Cu compounds of free-electron nature. The finite-temperature effect was included by accounting for the vibrational free energy within the Debye model. The present study shows that θ-Al2Cu is the ground state phase, agreeing with the experimental observations in the literature. The DFT + U approach could be useful to predict accurate formation energies of other Cu-containing precipitates in high-strength Al-alloys.