The core structure, recombination energy and Peierls energy for dislocations in Al

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Abstract:

In the framework of the Peierls model generalized to two dimensions the dissociation of a dislocation in the {111} plane of a fcc lattice into two Shockley partials is studied by a variational procedure. Each partial is made up by a distribution of infinitesimal dislocations with a density obtained by a superposition of three closely spaced Lorentz peaks of adjustable height, width and separation. The atomic misfit energy in the glide plane is obtained from the  surface represented by a two-dimensional Fourier series showing the symmetry of the {111} plane. The procedure is applied to Al for which a set of  values in the {111} plane has been obtained by Hartford et al. using ab-initio electron density functional theory. The dissociation width of the edge dislocation is found to be 0.74nm, which almost agrees with the experimental value of about 0.8nm. The screw dislocation is not split in the usual way but rather shows a widely extended core with some edge components. The energy to compress the core to apurescrew dislocation is Ec = 0.042eV/ b. The Peierls energy EP can be evaluated by numerical summation of the energy at the atom positions. However, contrary to previous treatments the core configuration has been relaxed and hence changes in elasticenergycontribute to EP. The result is not quite unambiguous.

Document Type: Research Article

DOI: http://dx.doi.org/10.1080/01418610108214434

Publication date: May 1, 2001

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