Rotational Diffusion in NaBH4

TitleRotational Diffusion in NaBH4
Publication TypeJournal Article
Year of Publication2009
AuthorsRemhof A, Lodziana Z, Buchter F, Martelli P, Pendolino F, Friedrichs O, Zuttel A, Embs JP
JournalJournal of Physical Chemistry C
Date PublishedSep 24
ISBN Number1932-7447
Accession Number
Keywordshydrogen-storage materials, nabd4, phase, sodium

Hydrogen dynamics in complex hydrides comprise long-range translational diffusion as well as localized motions like vibrations, librations, or rotations. All different motions are characterized by their specific length scale and time scales. Here we present a combined experimental and theoretical study oil the rotational diffusion of the (BH4)(-) ions in crystalline NaBH4. The motion is thermally activated and characterized by an activation energy of 117 meV and a prefactor of 11 fs. Thereby the motion is dominated by 90 degrees reorientations of the (BH4)(-) ion around the 4-fold symmetry axis of the cubic crystal. The experimental results are discussed oil the basis of DFT calculations, revealing the potential energy landscape of a (BH4)(-) subunit in the crystalline matrix.