Impurity effects on adhesion at an interface between NiAl and Mo

Fully self-consistent (LDA) density functional calculations have been perfo rmed to obtain the ideal adhesion energy and peak interfacial stress for ri gid fracture of an [001] interface between NiAl and Mo with and without int erfacial impurities. These calculations shed light on interfaces in NiAl-Mo eutectic composites in which [001] interfaces between NiAl (CsCl structure ) and Mo (b.c.c.) are prominent. In all cases impurities reduce the adhesio n energy, from 3.3 J/m(2) for the clean interface to 2.4, 1.5, and 1.4 J/m( 2) for C, O, and S impurities, respectively. Interestingly, however, C incr eases (40.0 GPa), while O (26.0 GPa) and S (18.0 GPa) decrease the peak int erfacial stress from that for the clean interface (37.0 GPa). The Harris fu nctional was also tested, and it was found that the ordering of adhesion en ergies and peak interfacial stresses were the same as for the fully self-co nsistent results, but errors in the magnitudes were significant. Misfit dis locations play an important role and are estimated to reduce the adhesion e nergy of the clean interface by an amount of the order of 10%. (C) 1999 Act a Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.