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 Thermal Conductivity of Polybutadiene Rubber from Molecular Dynamics Simulations and Measurements by the Heat Flow Meter Method

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7737
Author(s):  
Aleksandr Vasilev ◽  
Tommy Lorenz ◽  
Vikram G Kamble ◽  
Sven Wießner ◽  
Cornelia Breitkopf
Keyword(s):  
Molecular Dynamics ◽  
Heat Flow ◽  
Md Simulations ◽  
Flow Meter ◽  
Polybutadiene Rubber ◽  
Polymeric Chains ◽  
Dynamics Simulations ◽  
Heat Flow Meter ◽  
Good Agreement ◽  
Thermal Conductivities

Thermal conductivities of polybutadiene rubbers crosslinked by 2.4 and 2.8 phr of sulfur have been found to be functions of temperature via molecular dynamics (MD) simulations using the Green–Kubo method. From an analysis of the heat flux autocorrelation functions, it has been revealed that the dominant means of heat transport in rubbers is governed by deformations of polymeric chains. Thermal conductivities of rubber samples vulcanized by 2.4 and 2.8 phr of sulfur have been measured by the heat flow meter method between 0 ∘C and 60 ∘C at atmospheric pressure. The temperature dependencies of the thermal conductivities of rubbers and their glass transition temperatures derived from MD simulations are in good agreement with the literature and experimental data. Details are discussed in the paper.

Thermal Conductivity of Amorphous and Crystalline SiO2 Nano-Films from Molecular Dynamics Simulations

2012 ◽  
Vol 501 ◽  
pp. 64-69 ◽  
Author(s):  
Yan He ◽  
Yuan Zheng Tang ◽  
Man Ding ◽  
Lian Xiang Ma
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Film Thickness ◽  
Molecular Dynamics Simulations ◽  
Grain Morphology ◽  
Nonequilibrium Molecular Dynamics ◽  
Calculated Temperature ◽  
Dynamics Simulations ◽  
Different Thickness ◽  
Good Agreement

Normal thermal conductivity of amorphous and crystalline SiO2nano-films is calculated by nonequilibrium molecular dynamics (NEMD) simulations in the temperature range from 100 to 700K and thicknesses from 2 to 6nm. The calculated temperature and thickness dependences of thermal conductivity are in good agreement with previous literatures. In the same thickness, higher thermal conductivity is obtained for crystalline SiO2nano-films. And more importantly, for amorphous SiO2nano-films, thickness can be any direction of x, y, z-axis without effect on the normal thermal conductivity, for crystalline SiO2nano-films, the different thickness directions obtain different thermal conductivity results. The different results of amorphous and crystalline SiO2nano-films simply show that film thickness and grain morphology will cause different effects on thermal conductivity.

Thermal Conductivity of Silicon Thin Films Predicted by Molecular Dynamics Simulations and Theoretical Calculation

2011 ◽  
Vol 55-57 ◽  
pp. 1152-1155 ◽  
Author(s):  
Xing Li Zhang ◽  
Zhao Wei Sun
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Boltzmann Transport Equation ◽  
Phonon Transport ◽  
Dynamics Simulation ◽  
Boltzmann Transport ◽  
Silicon Thin Films ◽  
Simulation Results ◽  
Dynamics Simulations ◽  
Good Agreement

Molecular, dynamics simulation and the Boltzmann transport equation are used respectively to analyze the phonon transport in Si thin film. The MD result is in good agreement with the theoretical analysis values. The results show that the calculated thermal conductivity decreases almost linearly as the film thickness reduced and is almost independent of the temperature at the nanoscale. It was observed from the simulation results that there exists the obvious size effect on the thermal conductivity.

Prediction of Thermal Conductivity of Two-Dimensional Superlattices of Graphene and Boron Nitride by Equilibrium Molecular Dynamics

2015 ◽  
Author(s):  
Fernan Saiz ◽  
Carlos da Silva ◽  
Cristina H. Amon
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Boron Nitride ◽  
Heat Capacities ◽  
Two Dimensional ◽  
Electronic Band ◽  
Electronic Band Gap ◽  
Interface Orientation ◽  
Good Agreement ◽  
Thermal Conductivities

Graphene is a promising material to design faster microprocessors given its exceptionally high thermal conductivity. However, due to its null electronic band gap, graphene must be combined with high-electric conductivity materials such as boron nitride to manufacture competitive alternatives to traditional semiconductors. Thus, the goal of this study is to determine the thermal conductivities and heat capacities of two-dimensional superlattices of graphene and boron nitride as a function of the secondary periodicity and interface orientation. We apply the Green-Kubo method to atomic trajectories calculated with Molecular Dynamics to determine the thermal conductivities of superlattices with periodicities between one and five in the armchair and zigzag orientations at 300 K. Results show that conductivities increase with decreasing periodicity, in good agreement with predictions made with Harmonic Lattice Dynamics. Thermal conductivities parallel to the interface are significantly higher than those perpendicular to the interface in the armchair configuration and vice versa in the zigzag orientation. Moreover, the heat capacities are practically independent of the periodicity and interface orientation up to 1500 K.

Assessing the Validity of Quantum Corrections to Molecular Dynamics Simulations of Bulk Silicon

2011 ◽  
Vol 483 ◽  
pp. 653-657
Author(s):  
Qi Ming Zhou ◽  
Ke Dong Bi ◽  
Yun Fei Chen
Keyword(s):  
Molecular Dynamics ◽  
Theoretical Calculations ◽  
Md Simulations ◽  
Quantum Systems ◽  
Heat Fluxes ◽  
Quantum Corrections ◽  
Bulk Silicon ◽  
Theoretical Predictions ◽  
Dynamics Simulations ◽  
Thermal Conductivities

Thermal conductivities of bulk silicon are calculated by equilibrium molecular dynamics (MD) simulations. Applying common used quantum corrections to the MD results, does not bring them into better agreement with the theoretical predictions or experimental data, while the uncorrected values are closer to the theoretical predictions and experiments below 400K. By assessing the validity of quantum corrections according to theoretical calculations and MD simulations, we demonstrate that the hypothesis of equating the heat fluxes is not reliable. In addition, we explore that the rations of thermal conductivities of MD simulations and quantum calculations are approximate to 1. Then a modified quantum correction for mapping MD simulations to quantum systems is proposed.

Molecular Dynamics Simulations of Diffusive-Ballistic Heat Conduction in Carbon Nanotubes

2007 ◽  
Vol 1022 ◽  
Author(s):  
Junichiro Shiomi ◽  
Shigeo Maruyama
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Heat Conduction ◽  
Md Simulations ◽  
Gradual Transition ◽  
Length Dependence ◽  
Conductivity Profile ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations

AbstractHeat conduction of finite-length single-walled carbon nanotubes (SWNTs) has been studied by means of non-equilibrium molecular dynamics (MD) simulations. The length-dependence of the thermal conductivity was quantified for a range of nanotube-lengths at room temperature. The length dependence of thermal conductivity exhibits a gradual transition from nearly pure ballistic heat conduction to diffusive-ballistic heat conduction. The results show that the thermal conductivity profile does not converge even beyond a micrometer nanotube-length. Furthermore, the diameter dependence suggests that the phonon diffusion is reduced with the diameter.

Lanthanoids(III) and actinoids(III) in water: Diffusion coefficients and hydration enthalpies from polarizable molecular dynamics simulations

2012 ◽  
Vol 85 (1) ◽  
pp. 237-246 ◽  
Author(s):  
Fausto Martelli ◽  
Sacha Abadie ◽  
Jean-Pierre Simonin ◽  
Rodolphe Vuilleumier ◽  
Riccardo Spezia
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficients ◽  
Heavy Ions ◽  
Md Simulations ◽  
Contradictory Result ◽  
Dielectric Friction ◽  
Water Interaction ◽  
Diffusive Regime ◽  
Dynamics Simulations ◽  
Good Agreement

By using polarizable molecular dynamics (MD) simulations of lanthanoid(III) and actinoid(III) ions in water, we obtained ionic diffusion coefficients and hydration enthalpies for both series. These values are in good agreement with experiments. Simulations thus allow us to relate them to microscopic structure. In particular, across the series the diffusion coefficients decrease, reflecting the increase of ion–water interaction. Hydration enthalpies also show that interactions increase from light to heavy ions in agreement with experiment. The apparent contradictory result of the decrease of the diffusion coefficient with decreasing ionic radius is tentatively explained in terms of dielectric friction predominance on Stokes’ diffusive regime.

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.

Molecular Dynamics Simulations of Thermal Conductivity of Bi2Te3 Nanowires

2009 ◽  
Author(s):  
Bo Qiu ◽  
Lin Sun ◽  
Xiulin Ruan
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Surface Roughness ◽  
Smooth Surface ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Md Simulations ◽  
Interatomic Potentials ◽  
Phonon Confinement ◽  
Dynamics Simulations

In this paper, by employing the previously developed two-body interatomic potentials for bismuth telluride, molecular dynamics (MD) simulations are used to describe the thermoelectric properties, namely the lattice thermal conductivity, of Bi2Te3 nanowires. Cylindrical nanowires with both smooth surface and sawtooth surface roughness are studied, aiming at revealing the effects of phonon confinement in 1-D structures, phonon boundary scatterings and surface roughness on the lattice thermal conductivity of Bi2Te3 nanowires. In the end, the influence of various phonon scattering mechanisms on the nanostructures under study are summarized, possible paths to reduce lattice thermal conductivity in nanostructured Bi2Te3, which is favorable for enhancing thermoelectric performance, are pointed out.

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