MD simulation of lattice damage in graphite and its effects on the material properties

We investigate the possibility to bridge the macroscopic device behaviour and the nuclear scale damage occurring in very harsh conditions, experimentally unavailable environments such as the collimators which are present in the largest of the CERN accelerators, the HL-LHC. The function of these collimators is to intercept the particles of extremely high energy which deviate from their nominal trajectory.

We mainly employ a methodology proposed in the literature [1], the Frenkel Pair Accumulation (FPA): this is a computational shortcut to reproduce the radiation damage. Instead of computing and accumulating collisional cascades, on the assumption that primary damages produced by irradiation are point defects, it prescribes a continuous introduction of point defects in the material simulation box - in our case a graphite supercell. We implemented a similar methodology for the introduction of intercalated atoms (H and He) and their evolution within the material structure, both ‘unirradiated’ and ‘damaged’. Finally two different methods were used to study the responses to tensile stresses of pristine and “damaged” supercells, with or without gas.

We are now working on a different implementation of the FPA and the evolution of the supercell after the irradiation (aging, annealing). We usually run our simulation on the the Italian High Performance Computing center (CINECA).

This work is part of the research activity of the Work Package 17 of the ARIES collaboration, a Horizon 2020 project guided by CERN.

References

1. A. Chartier, L. Van Brutzel, B. Pannier, Ph. Baranek. Atomic scale mechanisms for the amorphisation of irradiated graphite. Carbon 91 (2015), 395-407