First-principles investigation on stability and mobility of hydrogen in α-Al2O3 (0001)/α-Cr2O3 (0001) interface

α-Al2O3 is representative coating materials of tritium permeation barriers. And it can be grown on α-Cr2O3 templates at a relatively low temperature by metal organic chemical vapor deposition. The α-Al2O3/α-Cr2O3 composite film can significantly suppress the deuterium permeation. However, the mechanism for diffusion of hydrogen in α-Al2O3/α-Cr2O3 interface is still unclear. In this work, the interface structure between α-Cr2O3 and α-Al2O3 in the hexagonal (0001) plane and its effect on stability and diffusion of hydrogen isotopes were studied based on the first principles. The thermodynamics and kinetics of hydrogen diffusion in α-Al2O3/α-Cr2O3 interface are also compared with the diffusion of hydrogen on (0001) plane α-Al2O3 and α-Cr2O3. The result shows that there exist hydrogen potential traps in the interface region and the migration of H atom can occur more readily in the α-Cr2O3 and α-Al2O3 bulk compared with the α-Al2O3 (0001)/α-Cr2O3 (0001) interface region. The highest barrier which comes from the diffusion of hydrogen from the α-Al2O3 part of the slab into the interface region is about 2.64 eV, indicating α-Al2O3 (0001)/α-Cr2O3 (0001) interface region is much more effective at suppressing hydrogen permeation.