Role of Phonon Dispersion in Lattice Thermal Conductivity Modeling

2004 ◽  
Vol 126 (3) ◽  
pp. 376-380 ◽  
Author(s):  
J. D. Chung ◽  
A. J. H. McGaughey ◽  
M. Kaviany
Keyword(s):  
Thermal Conductivity ◽  
Relaxation Time ◽  
Lattice Thermal Conductivity ◽  
Phonon Dispersion ◽  
Phonon Relaxation Time ◽  
Dynamics Simulations ◽  
Transfer Mechanisms ◽  
Conductivity Modeling ◽  
Fitting Parameters

The role of phonon dispersion in the prediction of the thermal conductivity of germanium between temperatures of 2 K and 1000 K is investigated using the Holland approach. If no dispersion is assumed, a large, nonphysical discontinuity is found in the transverse phonon relaxation time over the entire temperature range. However, this effect is masked in the final prediction of the thermal conductivity by the use of fitting parameters. As the treatment of the dispersion is refined, the magnitude of the discontinuity is reduced. At the same time, discrepancies between the high temperature predictions and experimental data become apparent, indicating that the assumed heat transfer mechanisms (i.e., the relaxation time models) are not sufficient to account for the expected thermal transport. Molecular dynamics simulations may be the most suitable tool available for addressing this issue.

The role of three-phonon Normal processes in the thermal conductivity of graphene

2012 ◽  
Vol 1404 ◽  
Author(s):  
Ayman Alofi ◽  
Gyaneshwar P. Srivastava
Keyword(s):  
Thermal Conductivity ◽  
Relaxation Time ◽  
Room Temperature ◽  
Phonon Dispersion ◽  
Correction Term ◽  
Single Mode ◽  
Analytical Expressions ◽  
Phonon Dispersion Relations ◽  
Time Theory

ABSTRACTWe have studied the thermal conductivity of graphene using Callaway’s effective relax-ation time theory and by employing analytical expressions for phonon dispersion relations and vibrational density of states based on the semicontinuum model by Nihira and Iwata. It is found that consideration of the momentum conserving nature of three-phonon Normal pro-cesses is very important for explaining the magnitude as well as the temperature dependence of the experimentally measured results. At room temperature, the N-drift contribution (the correction term in Callaway’s theory) provides 94% addition to the result obtained from the single-mode relaxation time theory, clearly suggesting that the single-mode relaxation time approach is inadequate for describing the phonon conductivity of graphene.

Lattice Thermal Conductivity Modelling of a Diatomic Nanoscale Material

2020 ◽  
Vol 10 (5) ◽  
pp. 602-609
Author(s):  
Adil H. Awad
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Correction Term ◽  
Nanoscale Material ◽  
New Approach ◽  
Two Samples ◽  
Conductivity Modelling ◽  
Callaway Model

Introduction: A new approach for expressing the lattice thermal conductivity of diatomic nanoscale materials is developed. Methods: The lattice thermal conductivity of two samples of GaAs nanobeam at 4-100K is calculated on the basis of monatomic dispersion relation. Phonons are scattered by nanobeam boundaries, point defects and other phonons via normal and Umklapp processes. Methods: A comparative study of the results of the present analysis and those obtained using Callaway formula is performed. We clearly demonstrate the importance of the utilised scattering mechanisms in lattice thermal conductivity by addressing the separate role of the phonon scattering relaxation rate. The formulas derived from the correction term are also presented, and their difference from Callaway model is evident. Furthermore their percentage contribution is sufficiently small to be neglected in calculating lattice thermal conductivity. Conclusion: Our model is successfully used to correlate the predicted lattice thermal conductivity with that of the experimental observation.

LATTICE THERMAL CONDUCTIVITY IN A HOLLOW SILICON NANOWIRE

2005 ◽  
Vol 19 (06) ◽  
pp. 1017-1027 ◽  
Author(s):  
WEI-QING HUANG ◽  
KE-QIU CHEN ◽  
Z. SHUAI ◽  
LINGLING WANG ◽  
WANGYU HU
Keyword(s):  
Thermal Conductivity ◽  
Relaxation Time ◽  
Lattice Thermal Conductivity ◽  
Silicon Nanowire ◽  
Boundary Scattering ◽  
Phonon Confinement ◽  
Time Approximation ◽  
Si Nanowire ◽  
Scattering Mechanisms ◽  
Relaxation Time Approximation

We theoretically investigate the lattice thermal conductivity of a hollow Si nanowire under the relaxation time approximation. The results show that the thermal conductivity in such structure is decreased markedly below the bulk value due to phonon confinement and boundary scattering. The thermal conductivities under different scattering mechanisms are given, and it is found that the boundary scattering is dominant resistive process for the decrease of the thermal conductivity.

scholarly journals Lattice thermal conductivity ofTixZryHf1−x−yNiSnhalf-Heusler alloys calculated from first principles: Key role of nature of phonon modes

2017 ◽  
Vol 95 (4) ◽  
Author(s):  
Simen N. H. Eliassen ◽  
Ankita Katre ◽  
Georg K. H. Madsen ◽  
Clas Persson ◽  
Ole Martin Løvvik ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
First Principles ◽  
Lattice Thermal Conductivity ◽  
Heusler Alloys ◽  
Phonon Modes

scholarly journals The role of excess Sn in Cu4Sn7S16 for modification of the band structure and a reduction in lattice thermal conductivity

2017 ◽  
Vol 5 (17) ◽  
pp. 4206-4213 ◽  
Author(s):  
Tongtong He ◽  
Naiming Lin ◽  
Zhengliang Du ◽  
Yimin Chao ◽  
Jiaolin Cui
Keyword(s):  
Thermal Conductivity ◽  
Band Structure ◽  
Lattice Thermal Conductivity ◽  
Band Structures

In this work, we have investigated the band structures of ternary Cu4Sn7+xS16 (x = 0–1.0) compounds with an excess of Sn, and examined their thermoelectric (TE) properties.

Superlattice Analysis for Tailored Thermal Transport Characteristics

2006 ◽  
Author(s):  
E. S. Landry ◽  
A. J. H. McGaughey ◽  
M. I. Hussein
Keyword(s):  
Thermal Conductivity ◽  
Thermal Transport ◽  
Direct Method ◽  
Continuum Theory ◽  
Lennard Jones ◽  
Constituent Species ◽  
The Cross ◽  
Dynamics Simulations ◽  
Superlattice Period

Molecular dynamics simulations and the Green-Kubo method are used to predict the thermal conductivity of binary Lennard-Jones superlattices and alloys. The superlattice thermal conductivity trends are in agreement with those obtained through the direct method, verifying that the Green-Kubo method can be used to examine thermal transport in heterostructures. The simulation temperature and the constituent species are fixed while the superlattice period structure is varied with the goals of (i) minimizing the cross-plane thermal conductivity and (ii) maximizing the ratio of in-plane to cross-plane thermal conductivities. The superlattice thermal conductivity in both the cross-plane and in-plane directions is found to be greater than the corresponding alloy value and less than the value predicted from continuum theory. The anisotropy of the thermal conductivity tensor is found to be at a maximum for a superlattice with a uniform layer thickness. Lattice dynamics calculations are used to investigate the role of optical phonons in the thermal transport.

Sign in / Sign up

Export Citation Format

Share Document