Atomistic simulations with slip boundary conditions - art. no. 144102

Dynamical variables are incorporated into Parrinello-Rahman simulations tha t allow for slipping of the simulation cell relative to its periodic images above and below a specified plane. Equations of motion are derived that sh ow the slip to be determined by the dynamical balance of an internal virial traction and an external glide force. Elements of the phenomenological the ory of martensitic transformations-namely, the existence of a habit plane a nd the fact that the macroscopic deformation of the new phase corresponds t o an invariant plane shear-arn introduced through the imposition of Lagrang ian constraints on the dynamics of the cell and slip variables. A model str uctural transformation is simulated with and without slip, and with rationa l and irrational habit planes. The allowance of slip with an irrational hab it plane dramatically lowers the barrier to the transformation. The results exhibit a remarkably wide variety of dislocation behavior, including edge and screw dislocations, slip, cross slip, dissociation, and twinning. An ex ample of the physical processes thought to be responsible for the rapid pro pagation of the phase transformation in steels and shape memory alloys-a gl issile dislocation interface-is also observed.