Dynamics of Pyramidal SiH3- Ions in ASiH(3) (A = K and Rb) Investigated with Quasielastic Neutron Scattering
Journal article, 2016

The two alkali silanides ASiH(3) (A = K and Rb) were investigated by means of quasielastic neutron scattering, both below and above the order-disorder phase transition occurring at around 275-300 K. Measurements upon heating show that there is a large change in the dynamics on going through the phase transition, whereas measurements upon cooling reveal a strong hysteresis due to undercooling of the disordered phase. The results show that the dynamics is associated with rotational diffusion of SiH3- anions, adequately modeled by H-jumps among 24 different jump locations radially distributed around the Si atom. The average relaxation time between successive jumps is of the order of subpicoseconds and exhibits a weak temperature dependence with a small difference in activation energy between the two materials, 39(1) meV for KSiH3 and 33(1) meV for RbSiH3. The pronounced SiH3- dynamics explains the high entropy observed in the disordered phase resulting in the low entropy variation for hydrogen absorption/desorption and hence the origin of these materials' favorable hydrogen storage properties.

aluminum hydrides



Materials Science


Science & Technology – Other Topics





potassium silanide


hydrogen-storage materials

borohydrides mbh4 m


Carin Österberg

Chalmers, Physics, Condensed Matter Physics

H. Fahlquist

Stockholm University

U. Haussermann

Stockholm University

C. M. Brown

National Institute of Standards and Technology (NIST)

Terrence J. Udovic

National Institute of Standards and Technology (NIST)

Maths Karlsson

Chalmers, Physics, Condensed Matter Physics

Journal of Physical Chemistry C

1932-7447 (ISSN) 1932-7455 (eISSN)

Vol. 120 12 6369-6376

Subject Categories

Physical Chemistry

Materials Chemistry



More information

Latest update