Recent molecular dynamics simulations of nanocrystals have illustrated the importance of stacking fault width for mechanical behavior and microstructure. Stacking fault width was a balance between elastic strain energy and the stacking fault energy. While the latter was a material constant, the former strain energy could vary due to local internal stresses thereby effecting stacking fault width. The presence and intensity of these stresses were functions of dislocation interactions in the crystal. Recent high resolution electron microscopy observations revealed a range of narrow stacking fault widths within grains of different sizes including those less than 10nm. In order to understand the reason for the presence of dislocations with small SF widths in metals, the reduction in stacking fault width due to dislocation stress screening was first demonstrated theoretically and numerically (molecular statics simulations). Various dislocation arrangements were examined, including a dislocation wall. Secondly, the reduction in stacking fault width in a thin film was examined via the introduction of free surfaces. These results revealed a wide variation in stacking fault widths, depending upon structure, and indicated that stress-screening was an important mechanism for creating the narrow widths which were observed experimentally.

Reductions in Stacking Fault Widths in FCC Crystals – Semi-Empirical Calculations. S.Aubry, D.A.Hughes: Physical Review B, 2006, 73[22], 224116 (15pp)