The interaction of a screw dislocation with point defects in bcc iron

Abstract

In this study, we calculate the interaction energy of intrinsic point defects vacancies and interstitials) with screw dislocations in body-centered cubic iron. First (we calculate the dipole tensor of a defect in the bulk crystal using molecular statics. Using a formulation based on linear elasticity theory, we calculate the interaction energy of the defect and the dislocation using both isotropic and anisotropic strain fields. Second, we perform atomistic calculations using molecular statics methods to directly calculate the interaction energy. Results from these two methods are compared. We verify that continuum methods alone are unable to correctly predict the interactions of defects and dislocations near the core. Although anisotropic theory agrees qualitatively with atomistics far from the core, it cannot predict which dumbbell orientations are stable and any continuum calculations must be used with caution. Spontaneous absorption by the core of both vacancies and dumbbells is seen. This paper demonstrates and discusses the differences between continuum and atomistic calculations of interaction energy between a dislocation core and a point defect.

Keywords:

• anisotropic elasticity
• atomic defects
• atomistic simulation
• defect structures
• dislocation interactions

Acknowledgements

The authors would like to thank Arthur Voter of Los Alamos National Laboratory for the use of his clsman atomistic code. This work was supported by DOE NEUP award DE-AC07-05ID14517 09-269 and LANL Sub-Contract Award Number 74230-001-09.

Notes

Note

1. It is important to make sure all calculations and comparisons are done in the same coordinate system. For example, dipole tensors are given in the crystal coordinate system, while strain fields are given, and atomistics are performed, in the dislocation coordinate system. First and second order tensors can be transformed between the crystal and dislocation systems by v ^C  = T v ^D , and where T is the transformation matrix, which contains the normalized vectors of the dislocation coordinate system as its columns.