Nonequilibrium versus equilibrium molecular dynamics for calculating the thermal conductivity of nanofluids

Nejatolahi, Mostafa; Golneshan, Ali Akbar; Kamali, Reza; Sabbaghi, Samad

doi:10.1007/s10973-020-09595-x

Cited by 17 publications

(3 citation statements)

References 66 publications

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“…In evaluating the thermal conductivity, [23] takes the equilibrium molecular dynamics (EMD) method while the present study applied the rNEMD method. Although the two approaches are physically equivalent, minor differences can be detected in the numerical results [53]. Moreover, the material parameters used in the simulations can also affect the final results.…”

Section: Numerical Results and Discussionmentioning

confidence: 99%

Effect of off-stoichiometry on the thermal conductivity of amorphous GeTe

Leng¹,

Wu²,

Lu³

et al. 2021

Phys. Scr.

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The reversible phase change of Germanium Telluride (GeTe) is essential for developing advanced non-volatile devices. We investigate off-stoichiometric effect on the thermal and structural properties of amorphous Ge$_{1-\delta}$Te (0 $\le$ $\delta$ $\le$ 0.12) via molecular dynamics. The structural optimization due to off-stoichiometry was taken into account with an empirical potential. Our simulated thermal conductivity is in the range of experimental observations. With increasing $\delta$, the thermal conductivity tends to be slightly reduced. Analysis on the coordinate number and the bond angle distribution indicates that the off-stoichiometric Ge$_{1-\delta}$Te still retain its ability of rapid phase transition. These results are helpful in reliable device design and modeling.

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Section: Numerical Results and Discussionmentioning

confidence: 99%

Effect of off-stoichiometry on the thermal conductivity of amorphous GeTe

Leng¹,

Wu²,

Lu³

et al. 2021

Phys. Scr.

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“…Green-Kubo formulation was previously experienced to deliver unrealistic κ enhancements in literature [55] as well as by the present authors [37]. Therefore, the Direct method κ evaluation is employed in the present study.…”

Section: Molecular Dynamics Methodsmentioning

confidence: 90%

Microscopic thermal characteristics of parallelly arranged nanowires in a liquid: the role of interface thermal resistance, solid-like liquid layer, and the restricted phonon transport

et al. 2023

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Nanofluids based on extended nanostructures, such as nanowires, have been demonstrated improved thermal conductivities (κ). However, the lack of a complete understanding at the microscopic level hinders the development of such nanofluids towards practical applications. We aim to provide it by investigating how the interface thermal resistance (Rb), ballistic phonon transport, and the solid-like liquid layer affect the heat conduction in nanowire based nanofluids. By employing Non-Equilibrium Molecular Dynamics (NEMD), it is found that the heat conduction in the parallelly arranged liquid and the nanowires exhibit a coupled thermal behavior owing to the Rb. This contradicts the predictions of the classical parallel heat conduction model, therefore, a novel model is proposed taking this coupled behavior into account. Using this model, it is shown that the high κ of the solid phase has a limited contribution to the effective κ of nanofluids having short nanowires due to the dominant Rb effect. For the case of long nanowires, however, the individual nanowire κ becomes a vital parameter defining the effective κ. Further, NEMD calculations reveal that the κ of suspended nanowires in a liquid is markedly reduced, questioning the validity of classical effective medium theories which use the bulk parameters. This reduction is attributed to surface atoms’ restricted vibrational freedom and the nanowire’s phonon-boundary scattering. By substituting this reduced κ of the solid phase into the new mathematical model, the theoretical predictions align closely with the NEMD calculations, exhibiting deviations below 10%. The sole contribution from the solid-like liquid layer to the κ enhancement lies between 20-30% in the nanofluids presently considered. Therefore, the findings of this study highlight the important roles played by the identified microscopic thermal characteristics in defining the effective κ for nanofluids based on nanowires.

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“…Nevertheless, the heat current expression in the Green–Kubo relation is a challenge for multicomponent systems because it is difficult to define the correct partial enthalpy term. 31 Nejatolahi et al 32 compared the EMD and NEMD methods by predicting the thermal conductivity of nanofluids of spherical copper nanoparticles. They found a significant discrepancy in the results between EMD and NEMD, and the results of NEMD were revealed to be more realistic.…”

Section: Introductionmentioning

confidence: 99%