Lu, GangKaxiras, Efthimios2019-09-202005Lu, Gang, and Efthimios Kaxiras. 2005. “Hydrogen Embrittlement of Aluminum: The Crucial Role of Vacancies.” Physical Review Letters 94 (15). https://doi.org/10.1103/physrevlett.94.155501.0031-90071079-71141092-0145http://nrs.harvard.edu/urn-3:HUL.InstRepos:41384115We report first-principles calculations which demonstrate that vacancies can combine with hydrogen impurities in bulk aluminum and play a crucial role in the embrittlement of this prototypical ductile solid. Our studies of hydrogen-induced vacancy superabundant formation and vacancy clusterization in aluminum lead to the conclusion that a large number of H atoms (up to 12) can be trapped at a single vacancy, which overcompensates the energy cost to form the defect. In the presence of trapped H atoms, three nearest-neighbor single vacancies which normally would repel each other, aggregate to form a trivacancy on the slip plane of Al, acting as embryos for microvoids and cracks and resulting in ductile rupture along these planes.en-USJournal Article2019-09-2010.1103/PhysRevLett.94.155501