Incorporation of γ-surface to phase field model of dislocations:: simulating dislocation dissociation in fcc crystals

Phase field method has become an attractive alternative to study dislocations of arbitrary configurations. Recently the model has been generalized for dislocation nodal reactions and network formation. Within the same framework, we study dissociation of various dislocation configurations into Shockley partials by incorporating directly gamma-surface data from ab initio calculations into the crystalline energy of the phase field model. The model is first validated against the generalized P-N model for dissociation of straight edge and screw dislocations in Al and Pd using the same sets of gamma-surface data and elastic constants. Then dissociation of dislocation nodes and a bent dislocation gliding on two intersecting {111} planes are investigated. The former leads to either an extended or a contracted node, depending on the directions of the sense vectors of the unit dislocations that join the node, while the latter leads to a stair-rod dislocation at the intersection of the two planes. With reliable ab initio gamma-surface data being calculated routinely by first principles, the extended phase field model could provide a flexible and realistic treatment of dissociation of dislocations of arbitrary configuration, interactions among extended dislocations, and creation and annihilation of various planar faults. (C) 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.