Vibrational properties of -KSiH3 and -RbSiH3: a combined Raman and inelastic neutron scattering study
Journal article, 2017

The hydrogen storage materials ASiH(3) (A=K and Rb) represent complex metal hydrides built from metal cations and pyramidal SiH3- ions. At room temperature, SiH3- moieties are randomly oriented because of dynamical disorder (-modifications). At temperatures below 200K, ASiH(3) exist as ordered low-temperature () modifications. The vibrational properties of -ASiH(3) were characterized by a combination of Raman spectroscopy and inelastic neutron scattering. Internal modes of SiH3- are observed in the spectral range 1800-1900cm(-1) (stretching modes) and 890-1000cm(-1) (bending modes). External modes are observed below 500cm(-1). Specifically, SiH3- librations are between 300-450cm(-1) and 270-400cm(-1) for A=K and Rb, respectively, SiH3- translations are between 95 and 160cm(-1), K+ translations are in the range 60-100cm(-1) and Rb+ translations in the range 50-70cm(-1). The red-shift of libration modes for A=Rb is associated with a 15-30% reduction of the libration force constants of SiH3- ions in -RbSiH3. This correlates with a lower temperature for the - order-disorder phase transition (278 vs 298K). Libration modes become significantly anharmonic with increasing temperature but are maintained up to at least 200K. The vibrational properties of ASiH(3) compare well to those of alkali metal borohydrides ABH(4) (A=Na-Cs).

order–disorder phase transition

alkali metal silanides

libration modes

complex metal hydrides

inelastic neutron scattering


Janos Mink

Hungarian Academy of Sciences

Pannon Egyetem

Yuan-Chih Lin

Chalmers, Physics, Condensed Matter Physics

Maths Karlsson

Chalmers, Physics, Condensed Matter Physics

Carin Österberg

Chalmers, Physics, Condensed Matter Physics

Terrence J. Udovic

National Institute of Standards and Technology (NIST)

H. Fahlquist

Stockholm University

Ulrich Häussermann

Stockholm University

Journal of Raman Spectroscopy

0377-0486 (ISSN) 1097-4555 (eISSN)

Vol. 48 2 284-291

Subject Categories

Physical Sciences

Areas of Advance

Materials Science



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