Swift heavy ions in polyethylene: simulation of damage formation along the path

TL;DR

This study uses atomic-level simulations to analyze damage formation in amorphous polyethylene caused by swift heavy ions, revealing the spatial distribution of damage and chemical fragments along the ion path.

Contribution

It combines Monte Carlo and molecular dynamics simulations to accurately model damage regions and chemical activity in polyethylene under swift heavy ion irradiation.

Findings

Maximum damage does not coincide with maximum energy loss point.

Thresholds for damage differ between ions with opposite Bragg curve shoulders.

Damage region size and shape depend on ion energy and trajectory.

Abstract

We present results of atomic-level simulations of damage formation along the paths of swift heavy ions (SHI) decelerated in the electronic stopping regime in amorphous polyethylene. The applied model combines the Monte-Carlo code TREKIS-3, which describes excitation of the electronic and atomic systems around the ion trajectory, with molecular dynamics simulations of the response of the atomic system to the excitation. The simulation results were used to reconstruct the damage configuration, shape and size of the damaged region. We demonstrated that the positions of the maximum energy loss and maximum damage on the ion trajectory do not coincide, being separated by more than 10 micrometers. The difference between the thresholds of damage production by ions with energies realizing the opposite shoulders of the Bragg curve of the electronic stopping was found. We also analyzed the spatial distribution of chemically active fragments of polyethylene chains formed around the ion trajectory as a function of SHI energy.