Free-surface effect on displacement cascades in BCC W: Molecular dynamics study

Hyung Gyu Lee, Sang Hyuk Yoo, Byeongchan Lee, Keonwook Kang

Research output: Contribution to journalArticlepeer-review

Abstract

We investigated the free-surface effect on displacement cascades in bcc tungsten using molecular dynamics simulations. Primary knock-on atom (PKA) is projected at different initial depths with two different projectile directions, inward and outward, to the surface. Compared to the bulk system, a simulation system with free surface contains increased number of remaining point defects and clustered defects at equilibrium. This pronounced defect production near the free surface is caused by the suppression of defect recombination events. The interstitials energetically favor the formation of adatoms at the free surface, and the nonsymmetric feature of interstitial mobility is responsible for active vacancy clustering at the sub-surface. The free surface effect extends to 8 and 4 nm in depth when the PKA projectile direction is outward and inward, respectively, with PKA energy of 30 keV at 400 K. Beyond this characteristic depth, the defect population and clustered fraction become similar to those in bulk system. Clustered vacancy develops into extended defects such as 〈100〉 and 〈111〉/2 vacancy loops. For the first time, immobile 〈111〉/2 dislocation is observed in PKA simulation, which is consistent with the experimental reports of both stable 〈100〉 and 〈111〉/2 dislocations of Mason et al (2014 J. Phys.: Condens. Matter. 26 375701).

Original languageEnglish
Article number126009
JournalNuclear Fusion
Volume60
Issue number12
DOIs
Publication statusPublished - 2020 Dec

Bibliographical note

Funding Information:
This research was supported by the Nuclear Fusion Research Program through the National Research Foundation of Korea (NRF) (2014M1A7A1A01030141, 2017M1A7A1A01016221).

Publisher Copyright:
© 2020 IAEA, Vienna

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

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