Materials Science

An Extended Jog

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Science  02 May 2008:
Vol. 320, Issue 5876, pp. 586
DOI: 10.1126/science.320.5876.586b

Radiation striking crystalline materials can damage their structure and related properties by generating vacancies (missing atoms) or interstitials (extra atoms stuffed between lattice sites). Demkowicz et al. use simulations to probe the effects of adding or removing atoms in copper-niobium multilayer nanocomposites. Two flaw-free interfaces can form between the Cu and Nb. The first occurs from the joining of the face-centered cubic Cu {111} plane and body-centered cubic Nb {110} plane. The second requires a straining and rotating of the Cu {111} to make it about 0.5% less dense in its interfacial area (Cuα). Under strain, screw and edge dislocations can form in the various layers, but of particular note, the screw dislocations can sit either at the Cu-Nb interface, or can shift into a Cu-Cuα interface. Thus, there are pathways for defects to move from the Nb into the Cu, for example. When an atom was removed from or added to the Cu layer, the authors found that instead of generating a localized defect, the atoms would reconstruct to form an extended jog (shown at left) that interacted and annihilated with existing screw dislocations. The efficient defect recombination suggests that materials designed to have similar interfaces to the Cu-Nb system could be useful for limiting damage from radiation exposure. — MSL

Phys. Rev. Lett. 100, 136102 (2008).

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