title: Rotational motion in LiBH4/LiI solid solutions.
abstract: We investigated the localized rotational diffusion of the (BH(4))(-) anions in LiBH(4)/LiI solid solutions by means of quasielastic and inelastic neutron scattering. The (BH(4))(-) motions are thermally activated and characterized by activation energies in the order of 40 meV. Typical dwell times between jumps are in the picosecond range at temperatures of about 200 K. The motion is dominated by 90° reorientations around the 4-fold symmetry axis of the tetrahedraly shaped (BH(4))(-) ions. As compared to the pure system, the presence of iodide markedly reduces activation energies and increases the rotational frequencies by more than a factor of 100. The addition of iodide lowers the transition temperature, stabilizing the disordered high temperature phase well below room temperature.
authors.affiliation: Empa Swiss Federal Laboratories for Materials Science and Technology, Hydrogen & Energy, 8600 Dübendorf, Switzerland. pascal.martelli@empa.ch
authors.forename: Pascal
authors.initials: P
authors.lastname: Martelli
authors.forename: Arndt
authors.initials: A
authors.lastname: Remhof
authors.forename: Andreas
authors.initials: A
authors.lastname: Borgschulte
authors.forename: Ralf
authors.initials: R
authors.lastname: Ackermann
authors.forename: Thierry
authors.initials: T
authors.lastname: Strässle
authors.forename: Jan Peter
authors.initials: JP
authors.lastname: Embs
authors.forename: Matthias
authors.initials: M
authors.lastname: Ernst
authors.forename: Motoaki
authors.initials: M
authors.lastname: Matsuo
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Orimo
authors.forename: Andreas
authors.initials: A
authors.lastname: Züttel