Nuclear magnetic resonance study of anion and cation dynamics in CsSiH3

In order to study the dynamical properties of cesium silanide CsSiH3, we have measured the H-1 and Cs-133 nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation rates in this compound over the temperature range of 5-354 K. The results of the H-1 NMR measurements indicate that [SiH3](-) anions in CsSiH3 retain unusually high reorientational mobility down to low temperatures. In particular, a significant narrowing of the proton NMR spectrum due to [SiH3](-) reorientations is observed in the range similar to 10-14 K. The order-disorder (beta ->alpha) phase transition accompanied by the strong acceleration of [SiH3](-) reorientations and by the change in the reorientational mechanism is observed above 200 K; according to the H-1 spin-lattice relaxation data, this transition appears to be gradual. For the high-temperature disordered alpha-phase, the activation energy for [SiH3]( )reorientations is found to be 41(4) meV. The Cs-133 NMR results are consistent with the onset of diffusive motion of Cs+ cations at the frequency scale of similar to 10(4) s(-1) above 300 K. (C) 2018 Elsevier B.V. All rights reserved.