Computer simulation of boundary effects on bubble growth in metals due to He.

Atomistic simulation methods were used to investigate and identify the relevant physical mechanisms necessary to describe the growth of helium gas bubbles within a metal lattice. Specifically, molecular dynamics simulations were performed to examine the material defects that originate from growing spherical He bubbles in a palladium crystal. These simulations consist of a model system containing bubbles within a metal and near a free surface. The simulation code employed was ParaDyn using the Embedded Atom Method to model the constitutive properties of Pd atoms in a FCC lattice. The results of these simulations are compared with previously run calculations of He bubbles in a bulk lattice [l]. These simulations show the influence of the free surface on defect creation and evolution. Features compared include the formation of inter-bubble dislocations, bubble pressure and swelling as functions of He to metal (He/M) concentration