The point defect properties in nearly stoichiometric B2 iron aluminides containing B were studied with density functional energetics and independent point-defect thermodynamics. The influences of temperature as well as of intrinsic and B complex point defects were investigated, together with those of the (S)LDA or (S)GGA frameworks. While confirming the importance of magnetism for a proper account of point defect properties, a strong binding between Al antisites (AlFe) and Fe vacancies (VFe) was revealed, together with vacancy formation energies that were markedly lower in SGGA than in SLDA. The [AlFe+VFe] complexes were found to exist in significant thermal amounts, and according to (S)GGA should also be structural defects. Moreover, B clearly appeared as a substitutional element, which argued against its usually assumed interstitial diffusion. In SLDA, it also exhibited non-negligible binding with Fe vacancies.

Influence of Complex Point Defects in Ordered Alloys - an ab initio Study of B2 Fe-Al-B. R.Besson, A.Legris, J.Morillo: Physical Review B, 2006, 74[9], 094103 (10pp)