Irradiation effects on the elastic properties of tungsten: Impact of dispersed He, vacancy, and transmutation solutes

The effects of irradiation on elastic properties of tungsten (W), crucial for predicting microstructure evolution and mechanical degradation in fusion environments, remains insufficiently characterized. Based on density-functional theory (DFT) simulations, the influence of vacancy (Vac) and substitutional helium (He) was investigated from three perspectives: local lattice distortion, charge density variation and Vac/He spatial configuration, with comparison to transmutation solutes. Results show that bulk modulus (B) and single-crystal shear modulus (C44) of W-X (X = Vac, He, solutes) systems positively correlate with the differential charge density accumulation between X and the first nearest neighboring W ions which represents bonding strength. In contrast, tetragonal shear modulus (C′) negatively correlates with the average of the absolute binding energy of X2 pairs formed from the third to tenth nearest-neighbor configurations, indicating that local lattice distortion induced by X weakens C′. For W-X (X = Vac, He) systems with nearly uniform X distributions, the spatial configuration of X significantly influences C′, C44 and polycrystalline shear modulus G at X contents above 2.78at.%, leading to marked expanding of variation ranges. Calculations based on Labusch’s theory reveal that dispersed Vac and substitutional He induce a hardening effect far exceeding that of alloying solutes.