ATOMISTIC SIMULATIONS OF THE STRUCTURE AND STABILITY OF PPV LOCKS IN AN L1(2) COMPOUND

The feasibility of conducting atomistic simulations of the ''PPV''-typ e locks in a(o)[110] screw superdislocations in L1(2) compounds was ex amined for the first time. Using an EAM potential fit to Ni3Al, PPV lo cks of heights h = b/2 and b were constructed, and their structure and energies calculated as a function of the length of the locked segment . The feasibility of simulating the PPV lock and estimating the activa tion energy for its nucleation under zero stress has been demonstrated . The activation enthalpy calculated from the present simulations for a jog height of h = b under zero stress was much larger than what can be estimated from experimental data on Ni3Al using models that rely on such locking. Limitations of the present work and suggestions for fut ure developments are discussed.