Place: 10 Years ICAMS - International Symposium, Ruhr-Universität Bochum, Germany
The segregation of hydrogen and silicon atoms in two high-angle symmetric tilt grain boundaries in transition metal Iridium are investigated using density functional theory simulations. Two distinct grain boundaries, Sig5(210) and Sig11(113), were chosen to study the segregation. Both the GBs show a contrasting behavior with respect to trapping sites of the impurity atoms: while the relatively loosely packed Sig5 GB has multiple low energy trapping sites, the close-packed Sig11 GB has very few. Even the behavior of the impurities is markedly different from each other, with Si showing a much stronger preference to segregate to the GBs than H.
In addition, a detailed analysis was done for one case where we studied the migration of H atom through the Sig5 GB and found that the open structure of the GB provides an easy migration path into the GB plane and a high energy barrier for reverse migration, effectively trapping the atom in the GB plane.