In classical modeling, solid solution hardening of alloys is attributed to mechanical stress fields around vacancies, substitutional atoms, dislocations, and precipitates, and to their influence on the elastic modulus of the alloy. In the present study, first-principles modelling of periodically repeated supercells allows us to go beyond this size argument and include also changes to the state of the electronic subsystem around defects of the crystal structure in aluminium alloys. The calculations were carried out using the DFT method in the GGA approximation using the ABINIT software package (www.abinit.org).

We systematically vary the relative arrangement of the defects within the supercell and the type of element included in the substitutional defect in order to provide data suitable for refining state-of-the-art machine learned potentials, which so far extend the traditional Hume-Rothery-based descriptors only by data from classical phase diagram calculations.

In particular, the lattice distortions around substitutional Mg, Zr, and Si atoms and around the vacancy site in crystalline aluminum, as well as their interactions, were analyzed using supercells of various sizes. The results indicate that the radius of the first coordination sphere changes within a range of ±1.5%. An in-depth analysis of lattice and electron density variations around an impurity atom indicates that all discernible changes in electron density are localized within the first coordination sphere surrounding the impurity. The calculation of the interaction between point defects indicates a potential tendency for the formation of MAl3 (M = Mg, Zr) precipitates, which may promote precipitation strengthening in Al-Mg-Zr-Si aluminium alloys. When the impurity atom is placed in the vicinity of an edge dislocation core additional contributions to the commonly applied classical ’size-stress’ theory are obtained, which show that the effect of electronic interactions needs to be included to refine the classical model.