Relaxation volumes of microscopic and mesoscopic irradiation-induced defects in tungsten

Daniel R. Mason (1) , Duc Nguyen-Manh (1, 2) , Mihai Cosmin Marinica (3) , Rebecca Alexander (4) , Andreea E. Sand (5) , Sergei L. Dudarev (1, 2)

1 CCFE - Culham Centre for Fusion Energy
2 Department of Materials
3 SRMP - Service de recherches de métallurgie physique
4 UMET - Unité Matériaux et Transformations - UMR 8207
5 Department of Physics [Helsinki]

The low energy structures of irradiation-induced defects in materials have been extensively studied over several decades, as these determine the available modes by which a defect can diffuse or relax, and how the microstructure of an irradiated material evolves as a function of temperature and time. Consequently many studies concern the relative energies of possible defect structures, and empirical potentials are commonly fitted to, or evaluated with respect to these. But recently [Dudarev et al. Nuclear Fusion 2018], we have shown that other parameters of defects not directly related to defect energies, namely their elastic dipole tensors and relaxation volumes, determine the stresses, strains and swelling of reactor components under irradiation. These elastic properties of defects have received comparatively little attention. In this study we compute relaxation volumes of irradiation-induced defects in tungsten using empirical potentials, and compare to density functional theory results. Different empirical potentials give different results, but some clear potential-independent trends can be identifed. We show that the relaxation volume of a small defect cluster can be predicted to within 10% from its point-defect count. For larger defect clusters we provide empirical fits as a function of defect cluster size. We demonstrate that the relaxation volume associated with a single primary-damage cascade can be estimated from the primary knock-on atom energy. We conclude that while annihilation of defects invariably reduces the total relaxation volume of the cascade debris, there is still no conclusive verdict about whether coalescence of defects reduces or increases the total relaxation volume.

Domains: Materials Science [cond-mat.mtrl-sci]; Computational Physics [physics.comp-ph]; Material chemistry

Daniel R. Mason, Duc Nguyen-Manh, Mihai Cosmin Marinica, Rebecca Alexander, Andreea E. Sand, et al.. Relaxation volumes of microscopic and mesoscopic irradiation-induced defects in tungsten. Journal of Applied Physics, 2019, 126, pp.074301. ⟨10.1063/1.5099165⟩. ⟨cea-03719920⟩