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Dynamics of Pyramidal SiH3u-^ Ions in ASiH3 (A = K and Rb) Investigated with Quasielastic Neutron Scattering



Carin Osterberg, Henrik Fahlquist, Ulrich Haussermann, Craig Brown, Terrence J. Udovic, Maths Karlsson


The two alkali silanides ASiH3 (A = K and Rb) were investigated by means of quasielastic neutron scattering, both below and above the order-disorder phase transition temperature occurring at around 200-250 K. Measurements upon heating show the onset of strong quasielastic scattering around the phase-transition temperature demonstrating that the phase-transition is dynamical in nature, whereas subsequent measurements upon cooling reveal a strong hysteresis. The results show that the dynamics is associated with rotational diffusion of SiH-3 anions, adequately moldeled by H-jumps amongst 24 different jump locations radially distributed around the Si atom. The average relaxation time between successive jumps is of order of subpicosecond 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.
Journal of Physical Chemistry C


Diffusion, Disordered Phase, Elastic Incoherent Structure Factor, Neutron Scattering, Quasielastic Neutron Scattering, Reorientational Motion, Rotations, Silanide, Silicide


Osterberg, C. , Fahlquist, H. , Haussermann, U. , Brown, C. , Udovic, T. and Karlsson, M. (2016), Dynamics of Pyramidal SiH<sub>3</sub>u-^ Ions in ASiH<sub>3</sub> (A = K and Rb) Investigated with Quasielastic Neutron Scattering, Journal of Physical Chemistry C, [online], (Accessed June 8, 2023)
Created March 3, 2016, Updated October 12, 2021