The Nature of BH4 – Reorientations in Hexagonal LiBH4

• Published in: Journal of physical chemistry. C Vol. 116; no. 1; pp. 1614 - 1618
• Main Authors: Verdal, Nina, Udovic, Terrence J, Rush, John J
• Format: Journal Article
• Language: English
• Published: Columbus, OH American Chemical Society 12.01.2012
• Subjects: C: Energy Conversion and Storage; Condensed matter: structure, mechanical and thermal properties; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Inorganic compounds; Physics; Solubility, segregation, and mixing; phase separation; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Hexagonal lattices; Hydrogen neutral atoms; Hydrogen storage; Hexagonal crystals; Structure factors; Solubility; Momentum; Quasi-elastic scattering; Hydrogen storage material; Crystal structure
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp211754g

Lithium borohydride (LiBH4) has lately been the subject of intense inquiry within the hydrogen storage community. Quasi-elastic neutron scattering spectra were measured for LiBH4 in the high-temperature hexagonal crystal phase. The elastic incoherent structure factor associated with the rapid BH4 – anion reorientations was determined at 400, 410, and 420 K for momentum transfers as high as 4.2 Å–1. The results strongly suggest a BH4 – reorientational mechanism approaching quasi-free, trigonal-axis rotation of three borohydride H atoms, combined with reorientational jump exchanges between these delocalized “orbiting” H atoms and the remaining axial borohydride H atom. This mechanism is consistent with previously reported diffraction and spectroscopy studies.