M. Gilbert (Sp), S.L. Dudarev, University of Oxford, Abingdon (UK); P.M. Derlet, Paul Scherrer
Institute, Villingen (Switzerland); D.G. Pettifor, University of Oxford, Abingdon (UK)
Tungsten and tungsten alloys are among the primary candidate materials for use in the plasma-facing first wall
and divertor components of ITER and fusion power plants. Consequently, it is vital to have an understanding of
how this metal behaves under irradiation. Using newly developed Finnis-Sinclair-type interatomic potentials [1, 2]
and molecular dynamics (MD) simulations, we investigated the behaviour of various vacancy-type defects that
form under the cascade-producing irradiation in tungsten and also iron for comparison. The atomic configurations
and formation energies of both spherical and planar voids were determined using lattice relaxation via molecular
statics. In addition to these defects, where open surfaces dominate formation energies, we have also studied
“collapsed” vacancy loops, of the kind observed experimentally.
The three defect types show a relationship between size and formation energy. For the void defects this relation is
controlled by the increase of surface energy with surface area, while for collapsed loops the formation energydefect
size curve has a more complex shape since elastic energy plays a significant role. A comparison of how the
relative stability of these different defects changes with size provides an explanation for experimental
observations of tungsten under irradiation.
This work is jointly funded by the Engineering and Physical Sciences Research Council and by EURATOM.
[1] P M Derlet, D Nguyen-Manh, and S L Dudarev, Crowdions in Body-Centred cubic Transition Metals, Phys. Rev.
B (2007) submitted for publication
[2] S L Dudarev, P M. Derlet, and C-H Woo, Driven Mobility of Self-Interstitial Defects under Electron Irradiation,
Nucl. Instrum. Meth. B (2007) in press