Effects of atomic grain boundary structures on primary radiation damage in alpha-Fe

A Esfandiarpour and SAH Feghhi and AA Shokri, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 362, 1-8 (2015).

DOI: 10.1016/j.nimb.2015.08.074

In this paper, we used five different grain boundary (GB) structures including two twists, two symmetric tilts and one asymmetric tilt for alpha-Fe, in order to study the influence of different GB structures on the production and time evolution of defects. Energetic behavior of point defects near GBs is investigated and analyzed using Molecular Static (MS) method to calculate and compare the "defect absorbency" of each structure. The primary radiation damage state near each GB structure is simulated using Molecular Dynamic (MD) method for 3 keV and 6 keV primary-knocked on atom (PKA) with velocity vector perpendicular to the GB plane at various distances in 300 K. We found that all five GB structures can decrease the defect number in bulk region, if cascade center locates on the GB plane (prefect overlap) and increase the vacancy number, if the overlap is imperfect. This depends on the energy of PKA and its distance from GB plane. Also, the results proved that the magnitude of the observed variations depends on the atomic structure of GB. Furthermore, the GBs that have stronger "interstitial absorbency" produce an excess concentration of vacancies in the bulk region, while the edge of the cascades overlaps with GB plane. This is the result of bigger "interstitial absorbency" of GBs in comparison with vacancies. (C) 2015 Elsevier B.V. All rights reserved.

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