Ab initio determination of free energies and derived properties (heat capacities, vacancies, solvus boundaries) for selected Al alloys containing Si, Mg and Cu

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This project continuous the efforts of the first funding period to derive thermodynamic properties of selected phases containing a subset of the elements Al-Si-Mg-Cu from first principles. We will make use of the already developed methodology to predict the free energy as a function of temperature, volume, and chemical composition. Previous simulations included besides quasiharmonic and electronic free energy contributions also the effect of anharmonic lattice vibrations and point defects (such as, e.g., vacancies). In the second funding period the methodology will be further developed in particular with respect to (i) the calculation of anharmonic contributions of alloys, (ii) the full free energy analysis for alloys with dilute impurity concentrations, and (iii) the consideration of chemical disorder on the investigated phases. Important systems in the analysis will be Cu-Si system, the Al-Cu-Si system and the Q phase. Similar to the first funding period the focus will be on the ab initio prediction of heat capacities, temperature dependent formation energies and concentration dependent solvus lines. For these quantities decisive new insights for the thermodynamic assessment with Calphad are expected, which can hardly be obtained from experiments.