The Crowdion

A crowdion is a (postulated) special low temperature configuration of interstitials in fcc metals.
For making a crowdion, image the row of atoms along a densely packed <111> direction. Now take a number of atoms - say 10 - and "crowd in" one more.
A kind of elongated interstitial along a <111> direction is obtained - a crowdion.
There was a big scientific controversy over the question if crowdions actually exist as a metastable interstitial configuration in the seventies. This controversy has never been finally resolved; however, most researchers in the field believe that it does not exist.
The advocates of crowdions came mainly from the Max-Planck-Institut für Metallforschung; Institut für Physik in Stuttgart; the opponents clusters around the research Center Jülich.
The following schematic drawing illustrates the crowdion configuration (for sake of clarity, the crowdion here is along <100 > in a cubic primitive crystal instead of <111>).

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go to 1.3.3 The larger View and Complications

© H. Föll (Defects - Script)