Atomic Motion in the Complex Hydride Li3(NH2)2I: 7Li and 1H Nuclear Magnetic Resonance Studies
journal contributionposted on 18.06.2015, 00:00 by Alexander V. Skripov, Roman V. Skoryunov, Alexei V. Soloninin, Olga A. Babanova, Motoaki Matsuo, Shin-ichi Orimo
To study the dynamical properties of the novel complex hydride Li3(NH2)2I showing fast-ion conduction, we have measured the 7Li and 1H NMR spectra and spin–lattice relaxation rates in this compound over broad ranges of temperature (98–488 K) and the resonance frequency (14–90 MHz). Our measurements have revealed two jump processes with different characteristic rates. The faster process corresponds to the three-dimensional translational diffusion of Li+ ions; the characteristic jump rate for this motion reaches ∼108 s–1 at 310 K. This Li+ diffusion process can be satisfactorily described in terms of a Gaussian distribution of the activation energies with the average Ead value of 0.38 eV. Comparison of the 7Li and 1H NMR data with the results of dipolar second moment calculations indicates that high Li+ mobility in Li3(NH2)2I is not related to the effects of NH2 reorientations. On the other hand, specific structural features of the Li-site sublattice in Li3(NH2)2I can facilitate fast Li+ diffusion. The slower jump process has been identified as the translational diffusion of intact NH2 groups. However, the characteristic jump rate for this process remains far below 108 s–1 up to 488 K.