HRPACK: a software describing the elastic fields near dislocations and interfaces at atomic scale

Abstract

High-resolution electron microscopy (HREM) observations is now enabling the displacement fields near crystalline defects in metals and alloys to be studied experimentally at atomic scale. A software package HRPACK has been conceived to simulate well-oriented defects visible in HREM images, assuming an elastic planar deformation field. Interactions between stacking faults, translation dislocations, Somigliana dislocations, facetted grain boundaries or stepped heterointerfaces containing possible misfit dislocations, can be depicted at atomic scale for any binary crystals. A precise representation of the atom column positions surrounding the singularities is compared with the experimental image. A theoretical atom box incorporating any chosen region of a defect is prepared in a suitable format to be straightforwardly readable by EMS, a multislice software presented by Stadelmann in 1987. Several examples involving the treatment of crystalline defect images are presented, namely, a stacking fault intersection in an fcc crystal, a triple node in GaAs formed by meeting faults and a nanotwin, misfit dislocations along a planar CdTe GaAs interface and along a complex cubic/orthorhombic interface. In the last example, related to a 90° misfit dislocation associated with an interfacial ledge, a simple route to a quantitative evaluation of the match between a digitized experimental image and the corresponding calculated elastic field is proposed. As a result, the visual inspection of the match gives an accuracy in the atom column positions close to 0.029 nm.