Generalized stacking-fault energetics and dislocation properties: Compact versus spread unit-dislocation structures in TiAl and CuAu

We present a general scheme for analyzing the structure and mobility of dislocations based on solutions of the Peierls-Nabarro model with a two component displacement field and restoring forces determined from the ab initio generalized stacking fault energetics (i.e., the so-called \ensuremath{\gamma} surface). The approach is used to investigate dislocations in ${L1}_{0}$ TiAl and CuAu; predicted differences in the unit dislocation properties are explicitly related with features of the \ensuremath{\gamma}-surface geometry. A unified description of compact, spread and split dislocation cores is provided with an important characteristic ``dissociation path'' revealed by this highly tractable scheme.