Effects of niobium solid-solution on cascade damage evolution in molybdenum-niobium alloys

Single crystal Molybdenum-Niobium (Mo-Nb) alloys serve as critical emitter materials for thermionic space nuclear reactors, where radiation-induced damage constitutes a fundamental constraint on their operational reliability. Molecular dynamics (MD) simulations on primary displacement cascades in pure Mo and Mo-Nb alloys reveal that high-energy PKAs (>30 keV) significantly promote Frenkel pair survival and defect cluster formation, while elevated temperatures suppress damage accumulation by accelerating defect migration and recombination. Nb solid-solution with low concentrations marginally increase stabilized defect density, whereas localized Nb segregation apparently amplifies intra-cascade defect production through preferential cluster nucleation. Notably, the minimal Nb incorporation in residual interstitial defects is driven by the prohibitively high formation energy of Nb-Nb dumbbells, rapid lattice re-incorporation kinetics of Nb interstitials, and suppressed interstitial mobility in Nb-containing systems. These findings establish an atomic-scale insight for radiation damage evolution in Mo-Nb alloys, demonstrating how Nb solid solution stability simultaneously regulates defect generation and clustering.