H2 desorption from LiH cluster and NH3 molecule studied by ab initio molecular dynamics simulation

We have performed ab initio, molecular dynamics simulations on proposed hydrogen storage system of lithium hydride (LiH) and ammonia (NH3), i.e., LiH + NH3 <-> LiNH2 + H-2 to clarify the microscopic mechanism of the hydrogen desorption for a system of one Li2H2 cluster and one NH3 molecule. We have shown, for the first time, the dynamical reaction process for the H-2 molecule formation from two H atoms, one of which is from the LiH cluster and the other is from the NH3, and each H atom of H-2 is not equivalent both in geometry and in charge during the reaction. The reaction model, regarding this H2 desorption as the only reaction process of hydrogen desorption from LiH and NH3, can explain the recent experiment for hydrogen desorption from LiD and LiNH2 by including the effects of reverse reactions. This model gives the ratios H-2:HD:D-2 and Li2NH:Li2ND close to those obtained by the experiment, and desorption profiles of H-2, HD and D-2 which qualitatively reproduce the characteristics of experimental profiles. (C) 2010 Elsevier B.V. All rights reserved.