Ab InitioStudy of H2Desorption from Magnesium Hydride MgH2Cluster

In the present study, we investigate H 2 desorption from a magnesium hydride MgH 2 cluster by performing total energy calculations based on the density functional theory (DFT). We calculate the potential energy surface (PES) for the H 2 desorption from a (MgH 2 ) 5 cluster. According to the total atomic charges of the Mg and H atoms at the initial (MgH 2 ) 5 cluster, the Mg–H bond is ionic-like. Because of this, the activation barrier for the H 2 desorption is considerably high (3.30 eV). Moreover, the structural relaxation for the system, allowing for only the two Mg atoms closest to the two desorbing H atoms, does not largely affect the potential energy of the system. The results indicate that the ionic-like Mg–H interaction is related to the thermodynamical stability of MgH 2 .