TY - JOUR
T1 - A quasielastic and inelastic neutron scattering study of the alkaline and alkaline-earth borohydrides LiBH4 and Mg(BH4)2 and the mixture LiBH4 + Mg(BH4)2
AU - Silvi, Luca
AU - Zhao-Karger, Zhirong
AU - Röhm, Eva
AU - Fichtner, Maximilian
AU - Petry, Winfried
AU - Lohstroh, Wiebke
N1 - Publisher Copyright:
This journal is © the Owner Societies.
PY - 2019
Y1 - 2019
N2 - Quasielastic neutron scattering was used to investigate the low energy transfer dynamics of the complex borohydrides Mg(BH4)2 in the α- and β-modifications, LiBH4 in the low and high temperature crystal structure, and an 1:1 molar mixture of LiBH4 + α-Mg(BH4)2. All investigated compounds show a rich dynamic behaviour below an energy range of ΔE = 10 meV with the superposition of rotational dynamics of the constituent [BH4]- anions and low lying lattice modes. For Mg(BH4)2, the rotational diffusion of the [BH4] units was found to be much more activated in the metastable β-polymorph compared to the α-phase, and the low lying lattice modes are even softer in the former crystal structure. In Mg(BH4)2, the structural phase transition is mainly governed by the lattice dynamics, while alkaline LiBH4 exhibits a transition of the [BH4] rotations around the phase transition temperature. Ball milled LiBH4 + α-Mg(BH4)2 remains a physical mixture of the parent compounds and each component retains its characteristic dynamic signature up to the melting temperature.
AB - Quasielastic neutron scattering was used to investigate the low energy transfer dynamics of the complex borohydrides Mg(BH4)2 in the α- and β-modifications, LiBH4 in the low and high temperature crystal structure, and an 1:1 molar mixture of LiBH4 + α-Mg(BH4)2. All investigated compounds show a rich dynamic behaviour below an energy range of ΔE = 10 meV with the superposition of rotational dynamics of the constituent [BH4]- anions and low lying lattice modes. For Mg(BH4)2, the rotational diffusion of the [BH4] units was found to be much more activated in the metastable β-polymorph compared to the α-phase, and the low lying lattice modes are even softer in the former crystal structure. In Mg(BH4)2, the structural phase transition is mainly governed by the lattice dynamics, while alkaline LiBH4 exhibits a transition of the [BH4] rotations around the phase transition temperature. Ball milled LiBH4 + α-Mg(BH4)2 remains a physical mixture of the parent compounds and each component retains its characteristic dynamic signature up to the melting temperature.
UR - http://www.scopus.com/inward/record.url?scp=85059361311&partnerID=8YFLogxK
U2 - 10.1039/c8cp04316g
DO - 10.1039/c8cp04316g
M3 - Article
C2 - 30543230
AN - SCOPUS:85059361311
SN - 1463-9076
VL - 21
SP - 718
EP - 728
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 2
ER -