Molecular Dynamics Simulation of Radiation Damage Using a Two - Temperature Model to Investigate Threshold Displacement Energies of Ni

Abstract

Nuclear reactors generate approximately ten percent of the world’s total electricity, making a significant contribution to the advancement of a low-carbon economy. However, the reactor core, where energy is generated, presents an extremely challenging environment for the materials used in these sections. They are exposed to high temperatures, mechanical stresses, and intense radiation. As a result, many materials have been studied, with particular focus on those that demonstrate excellent stability under thermal and irradiation conditions. Among the most promising candidates are Ni-based superalloys, which are widely used in reactor components due to their excellent mechanical strength, corrosion resistance, and radiation tolerance. A key example is the Fe-Ni-Cr alloy system, widely used in reactor structural components. However, despite their critical role in nuclear environments, the fundamental radiation damage mechanisms in these alloys are still not fully understood. To better understand the fundamental radiation damage processes in these alloys, it is essential to first investigate their primary constituent element, nickel. In this work, We determine the threshold displacement energy through the application of molecular dynamics simulations of pure Ni at both absolute zero and room temperature. Understanding nickel’s fundamental response to radiation damage begins with determining its threshold displacement energy. Calculating the threshold displacement energy of Ni will help identify its susceptibility to defect formation under irradiation, which is key to improving its radiation resistance. Once we gain insight into this property, it serves as a foundation for understanding how Ni-based super alloys respond to irradiation. This understanding will also be used to improve the performance of Ni-based alloys in irradiated environments, such as nuclear reactors. iv We have used the Bonny et al. [1], reparametrized embedded atomic model (EAM) potential in our simulations. Hereafter, we would be calling this potential Bonny-2011. The threshold values of FCC Ni at both absolute and room temperatures have been examined using the classical molecular dynamics (MD) method and the molecular dynamics two-temperature method (MD-TTM). Threshold values at 0 K using MD and MD-TTM have been calculated in the [111], [110] and [100] crystallographic directions. The results show clear directional dependence, with the lowest TDE observed along the [100] direction and the highest along the [110] direction when using classical MD. Incorporating electron- phonon coupling in MD-TTM produced systematically higher TDE values compared to classical MD, indicating enhanced susceptibility to defect formation when electronic effects are considered. Further directional dependence of TDE were examined against temperature using both methods and we found that, using MD-TTM produces higher values as compared to classical MD.