scholarly journals Crystalline polymers with exceptionally low thermal conductivity studied using molecular dynamics

2015 ◽  
Vol 107 (20) ◽  
pp. 201908 ◽  
Author(s):  
Andrew B. Robbins ◽  
Austin J. Minnich
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Low Thermal Conductivity ◽  
Crystalline Polymers

scholarly journals Ultra-low Thermal Conductivity in Si/Ge Hierarchical Superlattice Nanowire

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Xin Mu ◽  
Lili Wang ◽  
Xueming Yang ◽  
Pu Zhang ◽  
Albert C. To ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Silicon Germanium ◽  
Phonon Scattering ◽  
Low Thermal Conductivity ◽  
Structural Hierarchy ◽  
Si Nanowire ◽  
Hierarchical Structuring ◽  
Simulation Results ◽  
Dynamics Simulations

Abstract Due to interfacial phonon scattering and nanoscale size effect, silicon/germanium (Si/Ge) superlattice nanowire (SNW) can have very low thermal conductivity, which is very attractive for thermoelectrics. In this paper, we demonstrate using molecular dynamics simulations that the already low thermal conductivity of Si/Ge SNW can be further reduced by introducing hierarchical structure to form Si/Ge hierarchical superlattice nanowire (H-SNW). The structural hierarchy introduces defects to disrupt the periodicity of regular SNW and scatters coherent phonons, which are the key contributors to thermal transport in regular SNW. Our simulation results show that periodically arranged defects in Si/Ge H-SNW lead to a ~38% reduction of the already low thermal conductivity of regular Si/Ge SNW. By randomizing the arrangement of defects and imposing additional surface complexities to enhance phonon scattering, further reduction in thermal conductivity can be achieved. Compared to pure Si nanowire, the thermal conductivity reduction of Si/Ge H-SNW can be as large as ~95%. It is concluded that the hierarchical structuring is an effective way of reducing thermal conductivity significantly in SNW, which can be a promising path for improving the efficiency of Si/Ge-based SNW thermoelectrics.

The Effect of AIREBO on Thermal Conductivity of EPDM Networks

2013 ◽  
Vol 561 ◽  
pp. 164-168
Author(s):  
Lian Xiang Ma ◽  
Gang Yang ◽  
Yuan Zheng Tang ◽  
Yan He
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Bond Order ◽  
Low Thermal Conductivity ◽  
Lennard Jones ◽  
Torsion Potential ◽  
Dynamics Simulations

In this article, thermal conductivity of EPDM networks has been discussed using molecular dynamics simulations. The simulations are performed on four systems using adaptive intermolecular reactive empirical bond order (AIREBO) potential. The effect of Lennard-Jones (L-J) potential and torsion potential on thermal conductivity is discussed. The contribution of L-J potential to thermal conductivity is negative. However, contribution of torsion potential is positive. The results suggest that the randomly entanglement of molecular chains in EPDM networks is responsible for its low thermal conductivity.

Phonon Thermal Conductivity of the Cubic and Monoclinic Phases of Zirconia by Molecular Dynamics Simulation

2020 ◽  
Vol 843 ◽  
pp. 110-115
Author(s):  
Leila Momenzadeh ◽  
Irina V. Belova ◽  
Graeme E. Murch
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Lattice Thermal Conductivity ◽  
Dynamics Simulation ◽  
Heat Current ◽  
Phonon Thermal Conductivity ◽  
Low Thermal Conductivity ◽  
Two Phases

Zirconia has a number of remarkable properties, including a very low thermal conductivity. In this research, the phonon thermal conductivity of two phases (cubic and monoclinic) of zirconia (ZrO2) are calculated. For this purpose, an equilibrium molecular dynamics simulation employing the Green-Kubo formalism is used. The results are presented in detail over a wide temperature range, from 100 K to 2400 K and 100 K to 1400 K for the above-mentioned structures, respectively, with a 100K temperature step. The temperature dependence of the equilibrium atomic volume demonstrated a reasonable agreement with the experimental data. Moreover, the lattice thermal conductivity was calculated by analysing the heat current autocorrelation function. The results showed that zirconia has a low thermal conductivity that is dependent on the temperature. It was also shown that the lattice thermal conductivity of the two phases of zirconia can be decomposed into three contributions due to the acoustic shortrange and long-range phonon and optical phonon modes. Finally, the results from this research are compared with the available experimental data.

Structure and Thermoelectric Properties of New Quaternary Tin and Lead Bismuth Selenides, K1+xM4-2xBi7+xSe15 (M = Sn, Pb) and K1+xSn5-xBi11+xSe22

2000 ◽  
Vol 626 ◽  
Author(s):  
Antje Mrotzek ◽  
Kyoung-Shin Choi ◽  
Duck-Young Chung ◽  
Melissa A. Lane ◽  
John R. Ireland ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Single Crystal ◽  
Thermoelectric Properties ◽  
Three Dimensional ◽  
Structure Type ◽  
Narrow Gap ◽  
Low Thermal Conductivity ◽  
Seebeck Coefficients ◽  
Metal Atoms ◽  
Anionic Framework

ABSTRACTWe present the structure and thermoelectric properties of the new quaternary selenides K1+xM4–2xBi7+xSe15 (M = Sn, Pb) and K1-xSn5-xBi11+xSe22. The compounds K1+xM4-2xBi7+xSe15 (M= Sn, Pb) crystallize isostructural to A1+xPb4-2xSb7+xSe15 with A = K, Rb, while K1-xSn5-xBi11+xSe22 reveals a new structure type. In both structure types fragments of the Bi2Te3-type and the NaCl-type are connected to a three-dimensional anionic framework with K+ ions filled tunnels. The two structures vary by the size of the NaCl-type rods and are closely related to β-K2Bi8Se13 and K2.5Bi8.5Se14. The thermoelectric properties of K1+xM4-2xBi7+xSe15 (M = Sn, Pb) and K1-xSn5-xBi11+xSe22 were explored on single crystal and ingot samples. These compounds are narrow gap semiconductors and show n-type behavior with moderate Seebeck coefficients. They have very low thermal conductivity due to an extensive disorder of the metal atoms and possible “rattling” K+ ions.

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