DISSOCIATED DISLOCATIONS IN THE PEIERLS POTENTIAL

Dislocations in close-packed lattices dissociated in two partial dislo cations show a complex behaviour when moving over a periodic Peierls p otential. Several equilibrium states are possible, and the energy barr ier to motion of the combined system depends on the exact equilibrium separation of the partials, very sensitively so when they are strongly coupled. In this case the effective Peierls potential varies between zero and twice the potential for an individual partial. This mechanism may resolve an old discrepancy between low-temperature flow stress an d the Peierls stress as deduced from internal friction measurements.