Ab initio calculations for dissociative hydrogen adsorption on lithium oxide surfaces

摘要

Lithium ceramics are one class of materials being considered as tritium breeders for fusion technology,and hydrogen is known to enhance the release of tritium from lithium ceramic materials. Dissociative hydrogen chemisorption on the Li(sub 2)O surfaces of the (100), (110), and (111) planes has been investigated with ab initio Hartree-Fock calculations. Calculations for unrelaxed crystal Li(sub 2)O structures indicated that except for the (100) surface, the (110) and (111) surfaces are stable. Results on the heterolytic sites of n-layer (110) (where n (= or >) 2) slabs and three-layer (111) slabs suggest that dissociative hydrogen chemisorption is endothermic. For a one-layer (110) slab at 100% surface coverage, the dissociative hydrogen chemisorption is exothermic, forming OH(sup (minus)) and Li(sup +)H(sup (minus))Li(sup +). The results also indicate that the low coordination environment in surface step structures, such as kinks and ledges, may plan an important role in the hydrogen chemisorption process. On the homolytic sites of the (110) and (111) surfaces, there is no hydrogen chemisorption.