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Updated: Jun 3, 2026
Fabrication and Optimization of Type II Silicon Clathrate Films
Published on: October 14, 2025
A study of low-energy guest phonon modes in clathrate-II Na(x)Si136 (x = 3, 23, and 24)
M Beekman1, R P Hermann, A Möchel
1Department of Physics, University of South Florida, Tampa, FL 33620, USA.
Abstract:
Single-crystal x-ray diffraction from clathrate-II Na(x)Si(136) (x = 24) prepared by a new technique reveals the exceptionally large Na@Si(28) atomic displacement parameter (U(eq)) is strongly temperature dependent, and can be attributed to low-energy rattling modes associated with the Na guest. Inelastic neutron scattering (INS) spectra collected from Na(x)Si(136) powder specimens (x = 3, 23) confirm the presence of low-energy guest-derived phonon modes for Na@Si(28) and Na@Si(20). The lower energy Na@Si(28) rattler mode falls in the frequency range of the silicon host acoustic phonons, indicating the possibility for interaction with these phonons. The presence of these low-energy modes combined with the ability to controllably vary the guest content presents a unique opportunity for exploring the influence of guest-framework interactions on the lattice dynamics in intermetallic clathrates.
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