Electron Microscope Image Contrast from Small Dislocation Loops: III. Theoretical Predictions for Non-Edge Dislocation Loops in a BCC Crystal,
ATOMIC ENERGY RESEARCH ESTABLISHMENT HARWELL (ENGLAND)
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The theoretical study of image contrast from small finite dislocation loops in an isotropic bcc crystal, reported in Parts I and II Eyre et al 1977 a,b, has been extended to include non-edge loops. Computer image simulation has again been used to study the influence of loop normal, n, Burgers vector, b, diffraction vector, g, and image plane normal, z, on the distribution of black-white intensities in images from loops located in Layer 1, i.e. within 0.25 Epsilon g of the surface, where Epsilon g is the extinction distance for the diffracting vector g. As before, the choice and range of parameters have been determined by the authors interest in radiation damage in bcc molybdenum. The main conclusion from a survey of non-edge perfect loop images is that modifications are predicted to the images from edge loops on going to the non-edge configuration, but that in the majority of cases the scheme of image classification introduced for edge loops based on g.b is still appropriate.
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