Ammonia borane and lithium amidoborane proved to have potential as efficient hydrogen storage materials. Although a combination of both compounds, LiNH2BH3-NH3BH3 has been shown to have even better hydrogen release characteristics, the inherent process was not clear. We determined the reaction mechanism of H-2 release from LiNH2BH3-NH3BH3 using computational quantum chemistry methods (MP2 and CCSD(T) methods and aug-cc-pVnZ basis sets). The energy barrier for H-2 release becomes lower than in pure LiNH2BH3 or NH3BH3 in agreement with experiment. Relevant transition structures are analyzed in detail and the initial formation of a cyclic adduct is likely responsible for the strong reduction of energy barriers. (C) 2011 Elsevier B.V. All rights reserved.