• Sand, Andreea E.
• Nguyen-Manh, Duc
• Mason, Daniel R.
• Marinica, Mihai-Cosmin
• Alexander, Rebecca
• Dudarev, Sergei L.

Abstract

International audience ; The low energy structures of irradiation-induced defects in materials have been extensively studied overseveral decades, as these determine the available modes by which a defect can diffuse or relax, and how themicrostructure of an irradiated material evolves as a function of temperature and time. Consequently manystudies concern the relative energies of possible defect structures, and empirical potentials are commonlyfitted to, or evaluated with respect to these. But recently [Dudarev et al. Nuclear Fusion 2018], we haveshown that other parameters of defects not directly related to defect energies, namely their elastic dipoletensors and relaxation volumes, determine the stresses, strains and swelling of reactor components underirradiation. These elastic properties of defects have received comparatively little attention. In this studywe compute relaxation volumes of irradiation-induced defects in tungsten using empirical potentials, andcompare to density functional theory results. Different empirical potentials give different results, but someclear potential-independent trends can be identifed. We show that the relaxation volume of a small defectcluster can be predicted to within 10% from its point-defect count. For larger defect clusters we provideempirical fits as a function of defect cluster size. We demonstrate that the relaxation volume associated witha single primary-damage cascade can be estimated from the primary knock-on atom energy. We concludethat while annihilation of defects invariably reduces the total relaxation volume of the cascade debris, thereis still no conclusive verdict about whether coalescence of defects reduces or increases the total relaxation volume.

Topics

• density
• impedance spectroscopy
• cluster
• theory
• mass spectrometry
• defect
• density functional theory
• tungsten
• defect structure