Reorientational Dynamics in Y(BH4)3·xNH3 (x = 0, 3 and 7): The Impact of NH3 on BH4- Dynamics

Published

March 9, 2024

Author(s)

Jakob Grinderslev, Ulrich Haussermann, T. Jensen, Antonio Faraone, Michihiro Nagao, M. Karlsson, Terrence J. Udovic, M. Andersson

Abstract

The reorientational dynamics of Y(BH4)3·xNH3 (x = 0, 3, and 7) was studied using quasielastic neutron scattering (QENS) and neutron spin echo (NSE). The results showed that changing the number of NH3 ligands drastically alters the reorientational mobility of the BH4 − anion. From the QENS experiments, it was determined that the BH4 − anion performs 2-fold reorientations around the C2 axis in Y(BH4)3, 3-fold reorientations around the C3 axis in Y(BH4)3·3NH3, and either 2-fold reorientations around the C2 axis or 3-fold reorientations around the C3 axis in Y(BH4)3·7NH3. The relaxation time of the BH4 − anion at 300 K decreases from 2 × 10−7 s for x = 0 to 1 × 10−12 s for x = 3 and to 7 × 10−13 s for x = 7. In addition to the reorientational dynamics of the BH4 − anion, it was shown that the NH3 ligands exhibit 3-fold reorientations around the C3 axis in Y(BH4)3·3NH3 and Y(BH4)3·7NH3 as well as 3-fold quantum mechanical rotational tunneling around the same axis at 5 K. The new insights constitute a significant step toward understanding the relationship between the addition of ligands and the enhanced ionic conductivity observed in systems such as LiBH4·xNH3 and Mg(BH4)2·xCH3NH2.

Citation

Journal of Physical Chemistry C

Volume

128

Issue

11

Pub Type

Journals

Download Paper

https://doi.org/10.1021/acs.jpcc.4c00265

Local Download

Citation

Grinderslev, J. , Haussermann, U. , Jensen, T. , Faraone, A. , Nagao, M. , Karlsson, M. , Udovic, T. and Andersson, M. (2024), Reorientational Dynamics in Y(BH4)3·xNH3 (x = 0, 3 and 7): The Impact of NH3 on BH4- Dynamics, Journal of Physical Chemistry C, [online], https://doi.org/10.1021/acs.jpcc.4c00265, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=957278 (Accessed October 21, 2025)