The Dynamics of the Guests in Filled Germanium Clathrates

2005 ◽  
Vol 886 ◽  
Author(s):  
Raphael P. Hermann ◽  
Fernande Grandjean ◽  
Veerle Keppens ◽  
Werner Schweika ◽  
George S. Nolas ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Nuclear Inelastic Scattering ◽  
Vibrational Modes ◽  
Weakly Bound ◽  
Typical Time ◽  
Tunneling Dynamics ◽  
Time And Energy ◽  
Localized Vibrational Modes

ABSTRACTIn the filled gallium-germanium clathrates, R8Ga16Ge30, where R is Ba, Sr, or Eu, the guests are located in two large cages and are weakly bound to the crystalline clathrate framework. The caged guests exhibit a localized “rattling” vibrational mode that provides an efficient mechanism for reducing the thermal conductivity. Inelastic neutron scattering and nuclear inelastic scattering measurements have yielded the phonon density of states in R8Ga16Ge30; the line width of the localized vibrational modes is found to be an important parameter in determining the lattice thermal conductivity. Neutron diffraction studies on R8Ga16Ge30 have shown that the guests in the larger cage are located off-center, and it was proposed that their jumping about the four off-center locations is responsible for the observed glass-like thermal conductivity at temperatures below 10 K. The detection of such slow guest motion is challenging because the typical time and energy scales involved are ca. 4 ns and 1 µeV, respectively. We have studied the slow europium tunneling dynamics in Eu4Sr4Ga16Ge30 by both Mössbauer and microwave absorption spectroscopy.

scholarly journals Filled Skutterudite Antimonides: Validation of the Electron-Crystal Phonon-Glass Approach to New Thermoelectric Materials

1997 ◽  
Vol 478 ◽  
Author(s):  
D. Mandrus ◽  
B. C. Sales ◽  
V. Keppens ◽  
B. C. Chakoumakos ◽  
P. Dai ◽  
...  
Keyword(s):  
Specific Heat ◽  
Thermoelectric Materials ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Low Energy ◽  
Vibrational Modes ◽  
Weakly Bound ◽  
Filled Skutterudite ◽  
Resonant Ultrasound ◽  
Electron Crystal

AbstractAfter a brief review of the transport and thermoelectric properties of filled skutterudite antimonides, we present resonant ultrasound, specific heat, and inelastic neutron scattering results that establish the existence of two low-energy vibrational modes in the filled skutterudite LaFe3CoSb12. It is likely that at least one of these modes represents the localized, incoherent vibrations of the La ion in an oversized atomic “cage.” These results support the usefulness of weakly bound, “rattling” ions for the improvement of thermoelectric performance.

Anomalous vibrational modes in acetanilide as studied by inelastic neutron scattering

1992 ◽  
Vol 2 (10) ◽  
pp. 1929-1939 ◽  
Author(s):  
Mariette Barthes ◽  
Juegen Eckert ◽  
Susanna W. Johnson ◽  
Jacques Moret ◽  
Basil I. Swanson ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Vibrational Modes

Complete assignment of the vibrational modes of C60 by inelastic neutron scattering spectroscopy and periodic-DFT

2011 ◽  
Vol 13 (17) ◽  
pp. 7789 ◽  
Author(s):  
Stewart F. Parker ◽  
Stephen M. Bennington ◽  
Jon W. Taylor ◽  
Henryk Herman ◽  
Ian Silverwood ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Vibrational Modes ◽  
Complete Assignment ◽  
Inelastic Neutron Scattering Spectroscopy ◽  
Periodic Dft

The vibrational modes of vitreous B2O3: inelastic neutron scattering and modelling studies

1995 ◽  
Vol 182 (1-2) ◽  
pp. 78-89 ◽  
Author(s):  
Alex C. Hannon ◽  
Adrian C. Wright ◽  
John A. Blackman ◽  
Roger N. Sinclair
Keyword(s):  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Vibrational Modes ◽  
Modelling Studies

Impulse approximation neutron scattering from N2

1995 ◽  
Vol 73 (11-12) ◽  
pp. 772-778 ◽  
Author(s):  
R. A. Cowley ◽  
M. P. Zinkin ◽  
R. S. Eccleston ◽  
A. C. Evans ◽  
M. J. Harris
Keyword(s):  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Impulse Approximation ◽  
Inelastic Neutron ◽  
Vibrational Modes ◽  
Excitation Energies ◽  
Energy Transfers ◽  
Molecular Excitation ◽  
The Individual ◽  
Good Agreement

We present the results of a detailed investigation of the inelastic neutron scattering from diatomic N2, at wave-vector transfers in the range Q = 20–100 Å−1 (1Å = 10−10 m). At intermediate Q, the scattering shows structure arising from the vibrational modes of the molecule, while at large Q the scattering is well described by the impulse approximation for the individual atoms, despite the fact that the corresponding energy transfers are considerably less than the maximum molecular excitation energies. We find good agreement for all Q with a calculation incorporating the internal rotational and vibrational modes of the molecule explicitly.

Molecular Vibrations as the Origin of Solid State Effects in Borohydrides

2009 ◽  
Vol 1216 ◽  
Author(s):  
Andreas Borgschulte ◽  
Robin Gremaud ◽  
Florian Buchter ◽  
Zbigniew Lodziana ◽  
Andreas Züttel ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Solid State ◽  
Thermodynamic Properties ◽  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Vibrational Properties ◽  
Vibrational Modes ◽  
The Impact ◽  
Specific Phase

AbstractIn this proceeding, we discuss measurements of the vibrational properties of hydrides using inelastic neutron scattering (INS) and the impact of the vibrational modes on the thermodynamic properties. We compare the heat capacity of PdH0.63 and LiBH4 as measured calorimetrically to that derived form INS spectra. We show that the vibrational properties of Ca(BH4)2 depend on the specific phase and hitherto determine their stability.

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