Multiple hydrogen trapping at monovacancies

Novel structures for multiple hydrogen atoms trapped at a monovacancy are discussed. Using atomistic simulations based on semiempirical interatomic potentials and density functional theory, we find low-energy configurations for four, five, and six hydrogen atoms around a monovacancy different than those that have been previously studied in the literature. The energetics of hydrogen binding are compared to results, both theoretical and experimental, previously published in the literature. We argue that up to four hydrogen atoms may be exothermically bound to monovacancy.