7Li NMR and 35Cl, 81Br NQR Study of Lithium Ion Conductor LiAlX4 (X = Cl and Br)

Abstract

The dynamic behavior of LiAlX4 (X = Cl and Br) was studied by means of 7Li NMR and 35Cl, 81Br NQR spectroscopies. The motional narrowing processes of the 7Li NMR due to Li+ diffusion were observed above room temperature for single crystals of LiAlX4. The activation energies for these processes were 43.4 and 42.1 kJ mol−1 for the chloride and bromide analogs, respectively. A stepwise decrease in the 7Li NMR quadrupole splitting suggested that the Li nucleus sees time averaged electric field gradient (EFG) arising from several different sites. The modulation effect of Li+ diffusion on the NQR relaxation times was detected only for LiAlBr4 but not for the chloride analog.

Static and dynamic structures of CD3ND3GeCl3 studied by TOF high resolution neutron powder diffraction and solid state NMR

“…In general NQR relaxation rate (1/T 1 ) is represented by the sum of the following three contributions: Raman processes due to lattice vibrations, reorientation effects of the fragment containing the probe nucleus, and modulation effects of the efg tensor arising from a movable nearby fragment. [24][25][26] Apart from the anomalous behavior near the phase transition around 203 K, the observed relaxation rates (1/T 1 ) could be expressed using three contributions in units of s Ϫ1 as, where ω Q , qЈ/q and τ c are the angular NQR frequency, the fraction of the fluctuating efg, and the correlation time of the motion which obeys an Arrhenius relation, respectively. The first and second terms, corresponding to a Raman process and a reorientational motion of the isolated GeCl 3 Ϫ anion, are common for both analogs.…”

Structure and Dynamics of Li3InBr6 and NaInBr4 by Means of Nuclear Magnetic Resonance

“…The FWHM after the motional narrowing was reduced to 0.27 kHz, suggesting that diffusion of Na + occurred. By fitting (2) and (3) to these data, the activation energy was evaluated to be 62 kJ/mol. This value is much larger than that of the Li + diffusion.…”

“…We have already investigated the structure and dynamics of the compounds MBr-M'Br 3 (M = Li, Cu, Ag; M' = Al, Ga) [ 1,2]. In these compounds, the central metal M' is tetrahedrally coordinated by Br -ions.…”

Ab Initio Calculation of 81Br Nuclear Quadrupole Resonance Transition Frequencies for Brominated Aromatics (Flame Retardants)

“…The use of quantum chemical calculations to interpret nuclear magnetic resonance (NMR), nuclear quadrupole resonance (NQR), and gas-phase microwave spectra has a rich history. − Recent attention to NMR chemical shift calculations demonstrates a renewed interest for calculation of NMR properties. − Less attention has been focused on calculation of NQR transition frequencies, despite the widespread use of NQR spectroscopy in the study of materials containing 2 H, − 17 O, , 27 Al 1 , 14 N, 63 Cu/ 65 Cu, , 93 Nb, 35 Cl, ,, 209 Bi, 23 Na, and 81 Br. , Of particular interest in this work are brominated aromatics, including flame retardants, recently studied by 81 Br NQR spectroscopy . High-impact polystyrene (HIPS), used in manufacturing computer monitors, televisions, and business and electrical equipment, is made less flammable by the inclusion of up to 30% by mass brominated aromatics…”