O-LATTICE MODELING OF LEDGED, PARTIALLY COHERENT BCC-HCP BOUNDARIES

The structure of ledged, partially coherent b.c.c.:h.c.p. (beta:zeta) interfaces has been modeled by extending the Bollmann O-lattice theory to permit the matching of all atom positions in the two crystal structures and the matching between relaxed atom positions, each of which creates a set of additional O-points. Misfit-compensating ledges and structural ledges are predicted when interphase boundaries made up of parallel steps and terraces intersect additional O-points. Misfit-compensating ledges with Burgers (1100)(zeta)BAR//(211)(beta)BAR and Pitsch-Schrader (2110)(zeta)BAR//(100)(beta)BAR terraces have Burgers vectors and interledge spacings both one half those associated with misfit dislocations on the corresponding flat interfaces. Biatomic structural ledges with Burgers (1100)(zeta)BAR//(211)(beta)BAR and Potter (1101)(zeta)BAR//(101)(beta)BAR terraces are shown to have Burgers vectors and interledge spacings both one sixth of their misfit dislocation counterparts.