Molecular dynamics simulations of irradiation on microstructural and mechanical properties of 1,3,5-trinitro-1,3,5-triazacyclohexane

Abstract

Energetic materials are utilized in diverse conditions, including environments subject to neutron irradiation. Understanding the effects of irradiation on the microstructures and mechanical properties of energetic materials is crucial for their application in radiation-exposed settings. In this research, we have performed molecular dynamics (MD) simulations to study the irradiation effect on decomposition products, microstructures, and mechanical properties of 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX). The results showed that the irradiation damage to RDX primarily manifests in breaking chemical bonds, generating molecular fragments, and forming defects within the crystal. Specifically, as primary knock-on atom (PKA) energy increases, the number of broken chemical bonds shows an upward trend. Following a collision cascade, the primary products induced by irradiation were C₃H₆O₅N₆, NO₂, NO, H₂O, O₂, ·O, and ·OH radicals. An increase in the energy of the PKA was observed to enhance both the decomposition ratio of RDX and the total number of generated species. Furthermore, collision cascades significantly impact the mechanical properties of RDX, leading to a gradual decrease in both young's and shear modulus as decomposition progresses. This results in a reduction of hardness and stiffness, while the rise in Poisson's ratio, Cauchy pressure, and the B/G ratio suggests enhanced ductility. These findings provide a reference for understanding the microstructural damage and mechanical property changes of RDX induced by irradiation