Short-range dislocation interactions using molecular dynamics: Annihilation of screw dislocations
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Short-range dislocation interactions using molecular dynamics: Annihilation of screw dislocations S. Swaminarayan, R. LeSar, P. Lomdahl, and D. Beazley Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (Received 19 November 1997; accepted 26 June 1998)
We present results of a large-scale atomistic study of the annihilation of oppositely signed screw dislocations in an fcc metal using molecular dynamics (MD) and an Embedded-Atom-Method (EAM) potential for Cu. The mechanisms of the annihilation process are studied in detail. From the simulation results, we determined the interaction energy between the dislocations as a function of separation. These results are compared with predictions from linear elasticity to examine the onset of non-linear-elastic interactions. The applicability of heuristic models for annihilation of dislocations in large-scale dislocation dynamics simulations is discussed in the light of these results. I. INTRODUCTION
The mechanical, electrical, and optical properties of a material depend strongly on its microstructure, an important component of which is the dislocation substructure. To predict the properties of a material thus requires a knowledge of how the microstructure develops as a function of processing conditions and how that microstructure affects materials response. To calculate the microstructure, in this case the dislocation microstructure, requires a description of the interactions between dislocations. These interactions have two distinct regimes: (a) the linear-elastic regime (long-range interactions), which governs the behavior of dislocations separated by distances larger than a few Burgers vectors, and (b) the non-linear-elastic regime (short-range interactions), where the dislocation separations are small, displacements are large, and linear elasticity no longer applies. Although the long-range elastic interactions between dislocations are well known,1 there are no data available, either experimental or theoretical, that can be used to quantify the short-range forces and thus there are no accurate descriptions of them. A major uncertainty is the transition between the two regimes. Consequently, all large-scale studies of dislocation interactions2–5 have modeled the short-range interactions by utilizing simple heuristic rules. For example, most simulations have assumed that two dislocations of opposite sign annihilate each other when the distance between them becomes less than some critical distance, with no incorporation of the dynamics or mechanisms of the annihilation event. All other short-range effects, such as deviations from linear elasticity, are generally neglected. While atomistic simulations could provide direct information on short-range dislocation interactions, the difficulty in applying such methods to the large system sizes required for simulating the two (or more) dislocations has been a severe limitation. For a single dislocation embedded in a continuum, one can separate 3478
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