Limitations of meta-atom potential for analyzing dislocation core structure in TWIP steel

In recent years, the scheme of meta-atom interatomic interaction has been proposed and employed as a simple alternative to the complex potentials for multi-component alloys. Although this potential model has primarily been utilized for large-scale simulations of plastic deformation, the interpretation of structures and behaviors of individual line defects still needs to be explored. The major issue arises from the fact that the meta-atom model, and other such homogenization approaches, represent the real system only in a statistical sense over a critical length scale. As the descriptive spatial parameters for the structure of a dislocation may span from a few angstroms to tens of nanometers, it necessitates the examination of the transferability of meta-atom potential in this context. Here we analyze the core structures of dissociated and twinning dislocations in TWIP steel using the meta-atom force-field and variational Peierls-Nabarro model. In particular, we compute the core widths, stacking-fault widths, and Peierls stresses of dislocations. In addition, the impact of Escaig stress on the stacking fault ribbon has been explored. The analyses reveal the limitations of the meta-atom model in accurately revealing the structural features of dislocation cores. While the meta-atom scheme can provide a representative averaged-out value of the core width, it fails to show the statistical variations along the dislocation line. Similarly, the model misses the spatial fluctuation of critical negative Escaig shear stress, whereas its positive counterpart is reasonably represented.

Automated summary

The scheme of meta-atom interatomic interaction has been proposed as a simple alternative for complex potentials in multi-component alloys, however, its effectiveness in revealing the structural features of individual line defects in the real system remains to be explored. The study analyzes the core structures of dissociated and twinning dislocations in TWIP steel using the meta-atom force-field and variational Peierls-Nabarro model, revealing the limitations of the meta-atom model in accurately representing the statistical variations and spatial fluctuation of dislocation cores and negative Escaig shear stress.