A model of defect cluster creation in fragmented cascades in metals based on the cascade morphology analysis

A model of defect cluster creation in fragmented cascades in metals based on the cascade morphology analysis

A model of defect cluster creation in fragmented cascades in metals based on the cascade morphology analysis 150 150 UKAEA Opendata
UKAEA-CCFE-PR(20)74

A model of defect cluster creation in fragmented cascades in metals based on the cascade morphology analysis

The impacts of ions and neutrons in metals causes cascades of atomic collisions that expand and shrink, leaving microstructure defect debris, i.e. interstitial or vacancy clusters or loops of different sizes. In [A. De Backer, A. E. Sand, K. Nordlund, L. Lun´eville, D. Simeone, and S. L. Dudarev. EPL, 115(2):26001, 2016.], we described a method to detect the first morphological transition, i.e. the cascade fragmentation in subcascades, and a model of primary damage combining the Binary Collision Approximation (BCA) and Molecular dynamics (MD). In this paper including W, Fe, Be, Zr and 20 other metals, we demonstrate that the fragmentation energy increases with the atomic number and decreases with the atomic density following a unique power law. Above the fragmentation energy, the cascade morphology can be characterized by the cross pair correlation functions of the multitype point patterns formed by the subcascades. We derive the numbers of pairs of subcascades and observed that they follow broken power laws. The energy where the power law breaks indicates the second morphological transition when cascades are formed by branches decorated by chaplets of small subcascades. The subcascade interaction is introduced in our model of primary damage by adding pairwise terms. Using statistics obtained on hundreds of MD cascades in Fe, we demonstrate that the interaction of subcascades increases the proportion of large clusters in the damage created by high energy cascades. Finally, we predict the primary damage of 500 keV Fe ion in Fe and obtain cluster size distributions when large statistics of MD cascades are not feasible.

Collection:
Journals
Journal:
Journal of Physics: Condensed Matter
Publisher:
IOP (Institute of Physics)
Published date:
06/07/2018