Neutron scattering studies of the hydrogen storage material ammonia borane

Ammonia borane NH3BH3 has received a great deal of interest recently as a solid state hydrogen storage material since it was discovered to release hydrogen under mild thermal conditions. The unique di-hydrogen bonding interactions between the adjacent protic NH and hydridic BH groups control the dynamics of hydrogen motion and formation. In order to understand the fundamental interactions of the hydrogens in ammonia borane, quasielastic and inelastic neutron scattering techniques have been used to study the structure, phase transitions, vibrational spectroscopy, and rotational dynamics. The low frequency region of the neutron vibrational spectrum has been probed to investigate the nature of dihydrogen bonding in the ammonia borane solid and assignments have been made based on isotopic labeling and theory. Further, the proton rotational dynamics have been probed throughout the temperature range 10-300K to determine the nature of the proton motion as well as the rotational energy barrier.