Dynamics of Pyramidal SiH3- Ions in ASiH(3) (A = K and Rb) Investigated with Quasielastic Neutron Scattering
Artikel i vetenskaplig tidskrift, 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.

Materials Science

Science & Technology – Other Topics







aluminum hydrides

hydrogen-storage materials

potassium silanide

borohydrides mbh4 m




Carin Österberg

Chalmers, Fysik, Kondenserade materiens fysik

H. Fahlquist

Stockholms universitet

U. Haussermann

Stockholms universitet

C. M. Brown

NIST Center for Neutron Research

Terrence J. Udovic

NIST Center for Neutron Research

Maths Karlsson

Chalmers, Fysik, Kondenserade materiens fysik

Journal of Physical Chemistry C

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

Vol. 120 6369-6376


Fysikalisk kemi