Probing radiation resistance in simulated metallic core–shell nanoparticles

TRAMONTINA, D.R.; DELUIGI, O.R.; PINZÓN, R.; ROJAS-NUNEZ, J.; VALENCIA, F.J.; PASIANOT, R.C.; BALTAZAR, S.E.; GONZALEZ, R.I.; BRINGA, E.M.

COMPUTACIONAL MATERIALS SCIENCE

Elsevier

Año: 2023 vol. 227

0927-0256

We present molecular dynamics (MD) simulations of radiation damage in Fe nanoparticles (NP) and bimetallicFeCu core–shell nanoparticles (CSNP). The CSNP includes a perfect body-centered cubic (bcc) Fe core coatedwith a face-centered cubic (fcc) Cu shell. Irradiation with Fe Primary Knock-on Atoms (PKA) with energiesbetween 1 and 7 keV leads to point defects, without clustering beyond divacancies and very few slightly largervacancy clusters, and without interstitial clusters, unlike what happens in bulk at the same PKA energies. TheFe-Cu interface and shell can act as a defect sink, absorbing radiation-induced damage and, therefore, thefinal number of defects in the Fe core is significantly lower than in the Fe NP. In addition, the Cu shellsubstantially diminishes the number of sputtered Fe atoms, acting as a barrier for recoil ejection. Structurally,the Cu shell responds to the stress generated by the collision cascade by creating and destroying stacking faultsacross the shell width, which could also accommodate further irradiation defects. We compare our MD resultsto Monte Carlo Binary Collision Approximation (BCA) simulations using the SRIM code, for the irradiationof an amorphous 3-layer thin film with a thickness equal to the CSNP diameter. BCA does not include defectrecombination, so the number of Frenkel pairs is significantly higher than in MD, as expected. Sputtering yield(Y) is underestimated by BCA, which is also expected since the simulation is for a thin film at normal incidence.We also compare MD defect production to bulk predictions of the analytic Athermal Recombination CorrectedDisplacements Per Atom (arc-dpa) model. The number of vacancies in the Fe core is only slightly lower thanarc-dpa predictions, but the number of interstitials is reduced by about one order of magnitude compared tovacancies, at 5 keV. According to the radiation resistance found for FeCu CSNP in our simulations, this classof nanomaterial could be suitable for developing new radiation-resistant coatings, nanostructured components,and shields for use in extreme environments, for instance, in nuclear energy and astrophysical applications.