Computer analysis of dislocated spherical crystal surfaces

Abstract

The use of computer simulation as an aid to field-ion image interpretation has been extended to the case of dislocated crystals. The model chosen is a hemispherical, isotropic, b.c.c. crystal with a single dislocation passing through the centre of the sphere and emerging normal to the surface. Image forces have been neglected and classical elasticity theory has been used throughout. The variables in the programme are the direction and Burgers vector of the dislocation line, and the radius and thickness of the hemispherical shell. The results obtained confirm an analysis of dislocation contrast in field-ion images given by Pashley (1965) and Ranganathan (1966) and support the assumption that even for dislocated crystals the field evaporation end form is approximately hemispherical.