  Interplay between hydrogen and nanovoids, despite long-recognized as a
central aspect in hydrogen-induced damages in structural materials, remains
poorly understood. Focusing on tungsten as a model BCC system, the present
study, for the first time, explicitly demonstrated sequential adsorption of
hydrogen adatoms on Wigner-Seitz squares of nanovoids with distinct energy
levels. Interaction between hydrogen adatoms on the nanovoid surface is shown
to be dominated by pairwise power law repulsion. A predictive model was
established for quantitative prediction of configurations and energetics of
hydrogen adatoms in nanovoids. This model, further combined with equation of
states of hydrogen gas, enables prediction of hydrogen molecule formation in
nanovoids. Multiscale simulations based on the predictive model were performed,
showing excellent agreement with experiments. This work clarifies fundamental
physics and provides full-scale predictive model for hydrogen trapping and
bubbling in nanovoids, offering long-sought mechanistic insights crucial for
understanding hydrogen-induced damages in structural materials.
