Structural and dynamical trends in alkali-metal silanides characterized by neutron-scattering methods [electronic resource].
- Washington, D.C. : United States. Dept. of Energy. Office of Energy Efficiency and Renewable Energy, 2016.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy
- Physical Description:
- pages 21,218-21,227 : digital, PDF file
- Additional Creators:
- National Renewable Energy Laboratory (U.S.)
United States. Department of Energy. Office of Energy Efficiency and Renewable Energy
United States. Department of Energy. Office of Scientific and Technical Information
- Structural, vibrational, and dynamical properties of the mono- and mixed-alkali silanides (MSiH<sub>3</sub>, where M = K, Rb, Cs, K<sub>0.5</sub>Rb<sub>0.5</sub>, K<sub>0.5</sub>Cs<sub>0.5</sub>, and Rb<sub>0.5</sub>Cs<sub>0.5</sub>) were investigated by various neutron experiments, including neutron powder diffraction (NPD), neutron vibrational spectroscopy (NVS), neutron-scattering fixed-window scans (FWSs), and quasielastic neutron scattering (QENS) measurements. Structural characterization showed that the mixed compounds exhibit disordered (α) and ordered (β) phases for temperatures above and below about 200–250 K, respectively, in agreement with their monoalkali correspondents. Vibrational and dynamical properties are strongly influenced by the cation environment; in particular, there is a red shift in the band energies of the librational and bending modes with increasing lattice size as a result of changes in the bond lengths and force constants. Additionally, slightly broader spectral features are observed in the case of the mixed compounds, indicating the presence of structural disorder caused by the random distribution of the alkali-metal cations within the lattice. FWS measurements upon heating showed that there is a large increase in reorientational mobility as the systems go through the order–disorder (β–α) phase transition, and measurements upon cooling of the α-phase revealed the known strong hysteresis for reversion back to the β-phase. Interestingly, at a given temperature, among the different alkali silanide compounds, the relative reorientational mobilities of the SiH<sub>3</sub><sup>–</sup> anions in the α- and β-phases tended to decrease and increase, respectively, with increasing alkali-metal mass. Lastly, this dynamical result might provide some insights concerning the enthalpy–entropy compensation effect previously observed for these potentially promising hydrogen storage materials.
- Published through SciTech Connect.
Journal of Physical Chemistry. C 120 38 ISSN 1932-7447 AM
Wan Si Tang; Mirjana Dimitrievska; Jean -Noel Chotard; Wei Zhou; Raphael Janot; Alexander V. Skripov; Terrence J. Udovic.
- Funding Information:
View MARC record | catkey: 24045299