On the stability of nanovoids in fcc metals and the influence of hydrogen

Atomic-scale simulations are used to examine the stability of nanometric vacancy clusters in variety of face centered cubic metals (Au, Ag, Al, Cu and Ni), according to their shape, their size and the presence of hydrogen. It is shown that whilst in most of metals the stacking fault tetrahedron is the most stable defect in absence of hydrogen, cavities becomes more stable when the concentration of hydrogen is sufficiently large to cover the internal surfaces. The (100) surfaces are found to be the less energetic, which favors vacancy clusters with cuboid shape in the metals concerned here. The simulations are shown to agree well with theoretical predictions provided that the theory is parametrized with surface and bulk energies conformed to the atomistic models. The affinity between hydrogen and cuboid cavities has also been confirmed by the computation of hydrogen solubility, which is neatly enhanced in the vicinity of these cavities. Our study paves the way towards the comprehensive atomistic-based predictions for micro-structure in hydrogen-rich metals.