Atomic scale modeling of point defects in zirconium diboride

Simulations using density functional theory were carried out to investigate the defect properties of zirconium diboride (ZrB₂) and also the solution and diffusion of He and Li. Schottky and Frenkel intrinsic defect processes were all high energy as were mechanisms giving rise to nonstoichiometry; this has implications for high-temperature performance. Li and He species, formed by the transmutation of a ¹⁰B, should therefore mostly be accommodated at the resulting vacant B sites or interstitial sites. Because Li is considerably more stable at the vacant B sites, He will be accommodated interstitially. Furthermore, He was found to diffuse as an interstitial species through the lattice with a low activation energy. This would be consistent with He being lost from the ZrB₂ but with Li being retained to a much greater extent.