The elastic and magnetic properties, thermodynamical stability, deviation from stoichiometry and order/disorder transformations of phases that are relevant to Be alloys were investigated using density functional theory simulations coupled with phonon density of states calculations to capture temperature effects. A novel structure and composition were identified for the Be-Fe binary {\epsilon} phase. In absence of Al, FeBe_5 is predicted to form at equilibrium above ~ 1250 K, while the {\epsilon} phase is stable only below ~ 1650 K, and FeBe_2 is stable at all temperatures below melting. Small additions of Al are found to stabilise FeBe_5 over FeBe_2 and {\epsilon}, while at high Al content, AlFeBe_4 is predicted to form. Deviations from stoichiometric compositions are also considered and found to be important in the case of FeBe_5 and {\epsilon}. The propensity for disordered vs ordered structures is also important for AlFeBe_4 (which exhibits complete Al-Fe disordered at all temperatures) and FeBe_5 (which exhibits an order-disorder transition at ~ 950 K).
@article{arxiv.1407.5013,
title = {Crystal structure, thermodynamics, magnetics and disorder properties of Be-Fe-Al intermetallics},
author = {Patrick A. Burr and Simon C. Middleburgh and Robin W. Grimes},
journal= {arXiv preprint arXiv:1407.5013},
year = {2015}
}
Comments
14 pages, 10 figures, accepted for publication in J. Alloy Compd. on 14 March 2015