Size Effects in Green-Kubo and Direct Method Molecular Dynamics Predictions of Thermal Conductivity

2010 ◽  
Author(s):  
Daniel P. Sellan ◽  
Eric S. Landry ◽  
Joseph E. Turney ◽  
Alan J. H. McGaughey ◽  
Cristina H. Amon
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Direct Method ◽  
Direct Methods ◽  
System Size ◽  
Linear Extrapolation ◽  
Extrapolation Procedure ◽  
Dynamics Simulations ◽  
Minimum System ◽  
Thermal Conductivities

The bulk thermal conductivity of Lennard-Jones argon and Stillinger-Weber silicon is predicted using the Green-Kubo (GK) and direct methods in classical molecular dynamics simulations. While system-size independent thermal conductivities can be obtained with less than 1000 atoms for both materials using the GK method, the linear extrapolation procedure [Schelling et al. Phys. Rev. B 65, 144306 (2002)] must be applied to direct method results for multiple system sizes. It is found that applying the linear extrapolation procedure in a manner consistent with previous researchers can lead to an underprediction of the GK thermal conductivity (e.g., by a factor of 2.5 for Stillinger-Weber silicon at a temperature of 500 K). To understand this discrepancy, phonon properties are predicted from lattice dynamics calculations, and from these, length-dependent thermal conductivities. These results show that the linear extrapolation procedure is only accurate when the minimum system size used in the direct method simulations is comparable to the largest mean free paths of the phonons that dominate the thermal transport. This condition has not typically been satisfied in previous works.

scholarly journals Thermal Properties of Yttrium Aluminum Garnett From Molecular Dynamics Simulations

2011 ◽  
Author(s):  
Majid S. al-Dosari ◽  
D. G. Walker
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Specific Heat ◽  
Molecular Dynamics Simulations ◽  
Yttrium Aluminum Garnet ◽  
System Size ◽  
Yttrium Aluminum ◽  
Dynamics Simulations

Yttrium Aluminum Garnet (YAG, Y3Al5O12) and its varieties have applications in thermographic phosphors, lasing mediums, and thermal barriers. In this work, thermal properties of crystalline YAG where aluminum atoms are substituted with gallium atoms (Y3(Al1−xGax)5O12) are explored with molecular dynamics simulations. For YAG at 300K, the simulations gave values close to experimental values for constant-pressure specific heat, thermal expansion, and bulk thermal conductivity. For various values of x, the simulations predicted no change in thermal expansion, an increase in specific heat, and a decrease in thermal conductivity for x = 50%. Furthermore, the simulations predicted a decrease in thermal conductivity with decreasing system size.

Molecular Dynamics Prediction of the Thermal Conductivity of Si/Si1−xGex Superlattices

2007 ◽  
Author(s):  
E. S. Landry ◽  
A. J. H. McGaughey ◽  
M. I. Hussein
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Design Space ◽  
Direct Method ◽  
Preliminary Results ◽  
Dynamics Simulations ◽  
Weber Potential ◽  
Non Equilibrium

Molecular dynamics simulations and the non-equilibrium direct method are used to predict the effective cross-plane thermal conductivity of Si/Si1−xGex superlattices modeled by the Stillinger-Weber potential. The experimentally observed thermal conductivity design space and the methodology of making the thermal conductivity prediction with the direct method are reviewed. Preliminary results for the thermal conductivity prediction of a Si/Si0.7Ge0.3 at a temperature of 500 K are discussed.

Molecular Dynamics Prediction of the Thermal Conductivity of Si/Ge Superlattices

2007 ◽  
Author(s):  
E. S. Landry ◽  
A. J. H. McGaughey ◽  
M. I. Hussein
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Direct Method ◽  
Proper Selection ◽  
Dynamics Simulations ◽  
Weber Potential ◽  
Selection Of ◽  
Non Equilibrium

Molecular dynamics simulations and the non-equilibrium direct method are used to predict the thermal conductivity of a Si/Ge superlattice modeled by the Stillinger-Weber potential at a temperature of 300 K. We focus on the methodology of making the thermal conductivity prediction (limited effort has been made to model Si/Ge nanocomposites in the literature) and find that proper selection of the size and composition of the thermal reservoirs is important.

scholarly journals Thermal Conductivity of Polyisoprene and Polybutadiene from Molecular Dynamics Simulations and Transient Measurements

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1081 ◽  
Author(s):  
Aleksandr Vasilev ◽  
Tommy Lorenz ◽  
Cornelia Breitkopf
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Weight ◽  
Atmospheric Pressure ◽  
Md Simulations ◽  
Wire Method ◽  
Dynamics Simulations ◽  
Transient Measurements ◽  
Good Agreement ◽  
Thermal Conductivities

The thermal conductivities of untreated polyisoprene and polybutadiene were calculated by molecular dynamics (MD) simulations using a Green-Kubo approach between −10 °C and 50 °C at atmospheric pressure. For comparison, the thermal conductivities of untreated polyisoprene with a molecular weight of 54,000 g/mol and untreated polybutadiene with a molecular weight of 45,000 g/mol were measured by the transient hot wire method in similar conditions. The simulation results of both polymers are in good agreement with the experimental data. We observed that the MD simulations slightly overestimate the thermal conductivity due to the chosen force field description. Details are discussed in the paper.

scholarly journals Thermal Conductivities of Crosslinked Polyisoprene and Polybutadiene from Molecular Dynamics Simulations

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 315
Author(s):  
Aleksandr Vasilev ◽  
Tommy Lorenz ◽  
Cornelia Breitkopf
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Temperature Dependence ◽  
Molecular Dynamics Simulations ◽  
Md Simulations ◽  
Dynamics Simulations ◽  
First Time ◽  
Soft Rubber ◽  
Good Agreement ◽  
Thermal Conductivities

For the first time, the thermal conductivities of vulcanized polybutadiene and polyisoprene have been investigated according to their degree of crosslinking. The C-C and C-S-S-C crosslink bridges, which can be obtained via vulcanization processes using peroxides and sulfur, respectively, are considered. The temperature dependence of the thermal conductivity of soft rubber derived from molecular dynamics (MD) simulations is in very good agreement with the experimental results. The contributions of bonded and non-bonded interactions in the MD simulations and their influence on the thermal conductivities of polyisoprene and polybutadiene are presented. The details are discussed in this paper.

scholarly journals Molecular Dynamics Simulations of the Thermal Conductivity of Silicon-Germanium and Silicon-Germanium-Tin Alloys

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Zan Wang ◽  
X. Y. Cai ◽  
W. K. Zhao ◽  
H. Wang ◽  
Y. W. Ruan
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Silicon Germanium ◽  
Nonequilibrium Molecular Dynamics ◽  
Tin Alloys ◽  
Penetration Distance ◽  
Germanium Tin ◽  
Dynamics Simulations ◽  
Thermal Conductivities

In this work, we investigate the thermal conductivity properties of Si 1 − x Ge x and Si 0.8 Ge 0 Sn 2 y alloys. The equilibrium molecular dynamics (EMD) is employed to calculate the thermal conductivities of Si 1 − x Ge x alloys when x is different at temperatures ranging from 100 K to 1100 K. Then nonequilibrium molecular dynamics (NEMD) is used to study the relationships between y and the thermal conductivities of Si 0.8 Ge 0.2 Sn 2 y alloys. In this paper, Ge atoms are randomly doped, and tin atoms are doped in three distributing ways: random doping, complete doping, and bridge doping. The results show that the thermal conductivities of Si 1 − x Ge x alloys decrease first, then increase with the rise of x , and reach the lowest value when x changes from 0.4 to 0.5. No matter what the value of x is, the thermal conductivities of Si 1 − x Ge x alloys decrease with the increase of temperature. Thermal conductivities of Si 0.8 Ge 0.2 alloys can be significantly inhibited by doping an appropriate number of Sn atoms. For the random doping model, thermal conductivities of Si 0.8 Ge 0.2 Sn y alloys approach the lowest level when y is 0.10. Whether it is complete doping or bridge doping, thermal conductivities decrease with the increase of the number of doped layers. In addition, in the bridge doping model, both the number of Sn atoms in the [001] direction and the penetration distance of Sn atoms strongly influence thermal conductivities. The thermal conductivities of Si 0.8 Ge 0.2 Sn y alloys are positively associated with the number of Sn atoms in the [001] direction and the penetration distance of Sn atoms.

scholarly journals Ballistic Heat Transport in Nanocomposite: The Role of the Shape and Interconnection of Nanoinclusions

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1982
Author(s):  
Paul Desmarchelier ◽  
Alice Carré ◽  
Konstantinos Termentzidis ◽  
Anne Tanguy
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Free Path ◽  
Mean Free Path ◽  
Strong Increase ◽  
Moderate Increase ◽  
Energy Propagation ◽  
The Mean ◽  
Dynamics Simulations

In this article, the effect on the vibrational and thermal properties of gradually interconnected nanoinclusions embedded in an amorphous silicon matrix is studied using molecular dynamics simulations. The nanoinclusion arrangement ranges from an aligned sphere array to an interconnected mesh of nanowires. Wave-packet simulations scanning different polarizations and frequencies reveal that the interconnection of the nanoinclusions at constant volume fraction induces a strong increase of the mean free path of high frequency phonons, but does not affect the energy diffusivity. The mean free path and energy diffusivity are then used to estimate the thermal conductivity, showing an enhancement of the effective thermal conductivity due to the existence of crystalline structural interconnections. This enhancement is dominated by the ballistic transport of phonons. Equilibrium molecular dynamics simulations confirm the tendency, although less markedly. This leads to the observation that coherent energy propagation with a moderate increase of the thermal conductivity is possible. These findings could be useful for energy harvesting applications, thermal management or for mechanical information processing.

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