Molecular dynamics study of the material property changes induced by accumulated point defects in graphite

Abstract

Molecular dynamics simulations were performed on pristine graphite using an adaptive intermolecular reactive empirical bond-order (AIREBO) potential, which introduced various concentrations of point defects and different sizes in defect clusters. Induced by the accumulation of mono-vacancy and self-interstitial atoms (SIA), the changes to the geometry, density, Young’s modulus, fracture strength, and coefficient of thermal expansion (CTE) of graphite were simulated over a range of defect concentrations and cluster sizes. We found that accumulated Frenkel pairs lead to clearly-observed changes to the geometric and elastic properties in graphite crystal, but a relatively negligible effect on CTE. As expected, changing size of defect clusters with a given concentration relates to the variation of material properties. The property changes simulated in the present work are qualitatively consistent with the experimental observations. The results are expected to provide some insights into the link between cascade-induced point defects and experimentally irradiation-assisted material property changes.