PLANAR DISSOCIATIONS OF [101] SUPERDISLOCATIONS IN TIAL - AB-INITIO ELECTRON THEORY AND GENERALIZED PEIERLS-NABARRO MODEL

The planar configuration of the [10 (1) over bar] superdislocation in stoichiometric TiAl is determined with the generalized Peierls-Nabarro model using the gamma-surface energies calculated by the nb-initio el ectron theory. The displacement field is parametrized by a superpositi on of four partial Peierls dislocations. From the calculated separatio ns of the partials it is concluded that a weak-beam image of the [10 ( 1) over bar] superdislocation should resolve a superlattice intrinsic stacking-fault ribbon, whereas the complex stacking-fault (antiphase-b oundary) ribbon is at (beyond) the limit of the resolution.