STRUCTURE OF POINT-DEFECTS IN B2 FE-AL ALLOYS - AN ATOMISTIC STUDY BYSEMIEMPIRICAL SIMULATION

We present the first results of a simulation study of point-defect pro perties in B2 ordered Fe-Al alloys (34% < x(Al) < 52%). After examinin g the T = 0 K energetics of simple defects, we turn to complexes and d iscuss the usual hypothesis of independent elementary defects. Almost all complex defects involving an Al vacancy and an Al antisite atom in nearest neighbour position are shown to be unstable, confirming that Al vacancies are rare in these alloys. Small deviations from stoichiom etry induce a change in the nature of defects: whereas on the Al-rich side, isolated Al antisite atoms dominate, Fe antisite atoms have a st rong trend towards clustering on the Fe-rich side, lending to the form ation of local D0(3) order. Copyright (C) 1998 Elsevier Science B.V.