SEGREGATION TO AN (A(O) 2)[1(1)OVER-BAR-0] EDGE DISLOCATION IN CU0.1NI0.9/

Atomistic simulations of segregation to a dissociated (a(0)/2)[1(1) ov er bar0$] edge dislocation in the solid solution alloy Cu0.1Ni0.9 have been performed. Segregation to the stacking fault between the partial s is minimal. Results obtained with a general embedded atom method pot ential and one optimized for the Ni-Cu system differ significantly. Si mulations employing the optimized potentials show significantly more C u segregation to the dislocation cores than do simulations performed w ith the general potentials. When the general potentials are employed, the Cu concentration around the dislocation is well described using cl assical segregation isotherms based upon the stress distribution aroun d the dislocation, except in the dislocation core region. Deviations f rom the theoretically predicted segregation profile around the disloca tion core are largest along the slip plane. When the optimized potenti als are used, the deviations from the predicted segregation behavior a re significantly larger. The large deviations associated with the opti mized potentials were traced to the inadequacy of describing the local heat of segregation in terms of the elastic work sigma(h) Delta V. Th is can be rectified by adding a term to the heat of segregation that e xplicitly includes the composition dependence. The failure of the clas sical segregation isotherm to describe the segregation behavior around a dislocation is associated with non-ideal alloy thermodynamics and t he inadequacy of linear elasticity to appropriately describe the core region of the dislocation. The failure of the classical segregation is otherm within the core appears to result from the fact that the core a toms have different atomic coordination than those in the bulk materia l.