scholarly journals Localization of vibrational modes leads to reduced thermal conductivity of amorphous heterostructures

2018 ◽  
Vol 2 (5) ◽  
Author(s):  
Ashutosh Giri ◽  
Brian F. Donovan ◽  
Patrick E. Hopkins
2021 ◽  
Vol 5 (3) ◽  
Author(s):  
Jeffrey L. Braun ◽  
Sean W. King ◽  
Eric R. Hoglund ◽  
Mehrdad Abbasi Gharacheh ◽  
Ethan A. Scott ◽  
...  

2020 ◽  
Vol 6 (4) ◽  
pp. 723-728
Author(s):  
Jingyu Li ◽  
Peng-Fei Liu ◽  
Chi Zhang ◽  
Xiaobo Shi ◽  
Shujuan Jiang ◽  
...  

2005 ◽  
Vol 886 ◽  
Author(s):  
Raphael P. Hermann ◽  
Fernande Grandjean ◽  
Veerle Keppens ◽  
Werner Schweika ◽  
George S. Nolas ◽  
...  

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.


Science ◽  
2021 ◽  
pp. eabh1619
Author(s):  
Quinn D. Gibson ◽  
Tianqi Zhao ◽  
Luke M. Daniels ◽  
Helen C. Walker ◽  
Ramzy Daou ◽  
...  

The thermal conductivity of crystalline materials cannot be arbitrarily low as the intrinsic limit depends on the phonon dispersion. We used complementary strategies to suppress the contribution of the longitudinal and transverse phonons to heat transport in layered materials containing different types of intrinsic chemical interface. BiOCl and Bi2O2Se encapsulate these design principles for longitudinal and transverse modes respectively, and the bulk superlattice material Bi4O4SeCl2 combines these effects by ordering both interface types within its unit cell to reach an extremely low thermal conductivity of 0.1 W K−1 m−1 at room temperature along its stacking direction. This value comes within a factor of four of air. We demonstrated that chemical control of the spatial arrangement of distinct interfaces can synergically modify vibrational modes to minimize thermal conductivity.


2008 ◽  
Vol 8 (7) ◽  
pp. 3628-3651
Author(s):  
Deepak Srivastava ◽  
Maxim A. Makeev ◽  
Madhu Menon ◽  
Mohamed Osman

Representative results of computer simulation and/or modeling studies of the nanomechanical and thermal transport properties of an individual carbon nanotube, silicon nanowire, and silicon carbide nanowire systems have been reviewed and compared with available experimental observations. The investigated nanomechanical properties include different elastic moduli of carbon nanotubes, silicon nanowires, and silicon carbide nanowires, all obtained within their elastic limits. Moreover, atomistic mechanisms of elastic to plastic transition under external stresses and yielding of carbon nanotubes under experimentally feasible temperature and strain rate conditions are discussed in detail. The simulation and/or modeling results on thermal properties, presented in this work, include vibrational modes, thermal conductivity and heat pulse transport through single carbon nanotubes, and thermal conductivity of silicon nanowires.


2013 ◽  
Vol 1543 ◽  
pp. 71-79 ◽  
Author(s):  
Konstantinos TERMENTZIDIS ◽  
Arthur FRANCE-LANORD ◽  
Etienne BLANDRE ◽  
Tristan ALBARET ◽  
Samy MERABIA ◽  
...  

ABSTRACTThe thermal transport in amorphous/crystalline silicon superlattices with means of molecular dynamics is presented in the current study. The procedure used to build such structures is discussed. Then, thermal conductivity of various samples is studied as a function of the periodicity of regular superlattices and of the applied temperature. Preliminarily results show that for regular amorphous/crystalline superlattices, the amorphous regions control the heat transfer within the structures. Secondly, in the studied cases thermal conductivity weakly varies with the temperature. This, points out the presence of a majority of non-propagating vibrational modes in such systems.


Author(s):  
J. R. Romero-Arias ◽  
F. Salazar ◽  
G. G. Naumis ◽  
G. Fernandez-Anaya

We present a nonlinear model that allows exploration of the relationship between energy relaxation, thermal conductivity and the excess of low-frequency vibrational modes (LFVMs) that are present in glasses. The model is a chain of the Fermi–Pasta–Ulam (FPU) type, with nonlinear second neighbour springs added at random. We show that the time for relaxation is increased as LFVMs are removed, while the thermal conductivity diminishes. These results are important in order to understand the role of the cooling speed and thermal conductivity during glass transition. Also, the model provides evidence for the fundamental importance of LFVMs in the FPU problem.


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