FORMATION OF NANODISLOCATION DIPOLES IN SHOCK-COMPRESSED CRYSTALS

Molecular-dynamics modeling has been used to study the evolution of a dislocation nanostructure from the shock compression of a vacancy clus ter in a body-centered-cubic lattice. Detailed calculations have revea led the atomic displacements by which the clustered vacancies collapse . The energetics of the process were also monitored in detail. Stable [100] and [111] Burgers-vector dislocations have been identified in di pole configurations. These dislocations relate to a periodic nanodislo cation dipole structure proposed in a model by Armstrong, Miller, and Sandusky (AMS) to occur by the reaction of dislocations just behind th e shock front. The postshock stability of the AMS dipole nanostructure was also evaluated on a molecular-dynamics basis and the stress-strai n behaviors of the crystal for the pre- and postshock compression cond itions were compared.