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

Published

March 4, 2016

Author(s)

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

Abstract

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.

Citation

Journal of Physical Chemistry C

Volume

120

Issue

12

Pub Type

Journals

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Keywords

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

Citation

Osterberg, C. , Fahlquist, H. , Haussermann, U. , Brown, C. , Udovic, T. and Karlsson, M. (2016), Dynamics of Pyramidal SiH₃u-^ Ions in ASiH₃ (A = K and Rb) Investigated with Quasielastic Neutron Scattering, Journal of Physical Chemistry C, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=920274 (Accessed October 25, 2025)