Fig. 3: Data-driven surrogate model.

a Atomistic simulations generate data on deformation eigenstrains for a representative volume element under irradiation and external uniaxial stress. Radiation damage is simulated by assigning randomly chosen atoms in a tungsten crystal (white cutaway) recoil energies, drawn from scattering events with 20.3 MeV W⁶⁺ ions, leading to the initiation of collision cascades that result in the formation of nanoscale self-interstitial (red) and vacancy (blue) defects, shown here for 1 GPa. Eigenstrains are extracted in directions parallel (\({\varepsilon }_{{{\rm{MD}}},\parallel }^{* }\)) and perpendicular (\({\varepsilon }_{{{\rm{MD}}},\perp }^{* }\)) to the uniaxial stress direction. b A surrogate model is matched to the data using maximum likelihood estimation. Solid lines and shaded areas indicate the mean value and standard deviation, respectively, of eigenstrains from five repeated simulations per stress value. c The surrogate model, when adjusted to produce isotropic expansion at zero stress (see text), is in agreement with in situ measurements of elongation strain of tungsten irradiated by fission fragments at 20 K under tension.