scholarly journals Magnon and phonon dispersion, lifetime, and thermal conductivity of iron from spin-lattice dynamics simulations

2018 ◽  
Vol 123 (8) ◽  
pp. 085109 ◽  
Author(s):  
Xufei Wu ◽  
Zeyu Liu ◽  
Tengfei Luo
Keyword(s):  
Thermal Conductivity ◽  
Lattice Dynamics ◽  
Phonon Dispersion ◽  
Spin Lattice ◽  
Dynamics Simulations

Dielectric Nanocomposite Layering Configurations for Thermal Conductivity Reduction

2008 ◽  
Author(s):  
E. S. Landry ◽  
A. J. H. McGaughey ◽  
M. I. Hussein
Keyword(s):  
Thermal Conductivity ◽  
Phonon Dispersion ◽  
Phononic Crystal ◽  
Thermal Characteristics ◽  
Atomic Scale ◽  
Bulk Property ◽  
Space Applications ◽  
Structure And Property ◽  
Dynamics Simulations ◽  
Crystal Design

Thermal transport in crystals is governed by dynamic phenomena that take place at the atomic scale, namely phonon dispersion and scattering. A growing understanding of these mechanisms, coupled with increasingly capable nanofabrication and characterization technologies, provide a not-too-distant opportunity for designing a new class of materials with tailored thermal characteristics such as thermal conductivity, among other physical characteristics. Focusing on layered nanocomposites, also known as superlattices, modeled using the Lennard-Jones potential as a starting platform, we examine the effects of layering topology on the bulk property of thermal conductivity. We use molecular dynamics simulations to examine the link between structure and property; and employ ideas from phononic crystal design to investigate the potential of realizing dielectric crystals with exceedingly low thermal conductivities. This work potentially targets a range of applications such as thermal insulators for space applications and thermoelectrics for energy harvesting.

Argon Thermal Conductivity by Anharmonic Lattice Dynamics Calculations

2008 ◽  
Author(s):  
J. E. Turney ◽  
A. J. H. McGaughey ◽  
C. H. Amon
Keyword(s):  
Thermal Conductivity ◽  
Thermal Transport ◽  
Lattice Dynamics ◽  
Mode Shapes ◽  
Face Centered Cubic ◽  
Phonon Modes ◽  
Anharmonic Lattice ◽  
The Face ◽  
Face Centered ◽  
Dynamics Simulations

Lattice dynamics calculations are used to investigate thermal transport in the face-centered cubic Lennard-Jones (LJ) argon crystal between temperatures of 20 and 80 K. First, quasi-harmonic lattice dynamics calculations are used to find the frequencies and mode shapes of non-interacting phonons [1]. This information is then used as input for anharmonic lattice dynamics calculations. Anharmonic lattice dynamics is a means of computing the frequency shift and lifetime of each phonon mode due to interactions with other phonons [2]. The phonon frequencies, group velocities, and lifetimes, determined with the lattice dynamics methods, are then used to compute the thermal conductivity. The thermal conductivities predicted by the lattice dynamics methods are compared to predictions from molecular dynamics simulations. The two methods are found to agree well at low temperature but diverge at higher temperatures (i.e., near the melting point). The properties of individual phonon modes are used to identify the modes that dominate thermal transport.

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.

Thin Film Thermal Conductivity by Anharmonic Lattice Dynamics Calculations

2008 ◽  
Author(s):  
J. E. Turney ◽  
A. J. H. McGaughey ◽  
C. H. Amon
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Thermal Conductivity ◽  
Lattice Dynamics ◽  
Phonon Mode ◽  
Mode Shapes ◽  
Bulk Crystals ◽  
Anharmonic Lattice ◽  
Dynamics Simulations ◽  
Group Velocities

Lattice dynamics calculations are used to investigate thermal transport in argon thin films with thicknesses ranging between one and ten nanometers. Quasi-harmonic lattice dynamics calculations are used to find the frequencies and mode shapes of non-interacting phonons. This information is then used as input for anharmonic lattice dynamics calculations, whereby we compute the frequency shift and lifetime of each phonon mode due to interactions with other phonons. The phonon frequencies, group velocities, and lifetimes determined with the lattice dynamics techniques are then used to compute the in-plane thermal conductivity of the thin films as a function of film thickness. The thermal conductivities predicted by the lattice dynamics methods are compared to predictions from molecular dynamics simulations. Differences in the phonon characteristics in thin films compared to bulk crystals are examined by comparing the contribution to the thermal conductivity as a function of frequency.

Phonon heat transport properties of graphene based on molecular dynamics simulations and lattice dynamics

2019 ◽  
Vol 33 (05) ◽  
pp. 1950020
Author(s):  
Zhixin Hui ◽  
Yufeng Chang
Keyword(s):  
Molecular Dynamics ◽  
Lattice Dynamics ◽  
Phonon Dispersion ◽  
Nonequilibrium Molecular Dynamics ◽  
Dynamical Matrix ◽  
System Temperature ◽  
Heat Transport Properties ◽  
The One ◽  
Dynamics Simulations ◽  
Experimental Researches

To choose an ideal method to study the phonon properties of graphene, the results of thermal conductivity (TC) of graphene computed using the equilibrium molecular dynamics (EMD), reverse nonequilibrium molecular dynamics (RNEMD) and direct nonequilibrium molecular dynamics (DNEMD) with Tersoff potential are compared, and we find that all of them are very close to each other. While two of them have been compared in the past, there is a lack of comparison of the three methods. Eventually, we choose the Green–Kubo method to study the temperature dependence of TC in graphene and find that the [Formula: see text] diverges with the system temperature T as [Formula: see text]T[Formula: see text] with [Formula: see text] and [Formula: see text] for the direction of armchair and zigzag, respectively, which is in reasonable agreement with the one in recent theoretical and experimental researches. To gain further insight into the TC, the phonon dispersion and the phonon density of states (PDOS), which depend on evaluating the eigenvalues and the eigenvectors of dynamical matrix, are calculated for graphene with dimensions of 30 × 30 unit cell by a combination of EMD simulations and lattice dynamics calculations.

Spin-Lattice Dynamics Simulations of Ferromagnetic Iron

2008 ◽  
Author(s):  
Pui-Wai Ma ◽  
C. H. Woo ◽  
S. L. Dudarev ◽  
Anatoly S. Avilov ◽  
Sergei L. Dudarev ◽  
...  
Keyword(s):  
Lattice Dynamics ◽  
Spin Lattice ◽  
Ferromagnetic Iron ◽  
Dynamics Simulations
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