Understanding the mechanism of diffuse phonon scattering at disordered surfaces by atomistic wave-packet investigation

Shao, Cong; Rong, Qingyuan; Li, Nianbei; Bao, Hua

doi:10.1103/physrevb.98.155418

Cited by 40 publications

(22 citation statements)

References 63 publications

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“…10(b)], we add 2.2-nm amorphous silicon between the thermal reservoirs and the fixed layers to generate diffuse phonon scattering. Recent wave packet simulations have clearly shown that a flat crystalline surface specularly scatters phonons while amorphous silicon induces strong diffuse scattering [63]. The third configuration is the same as in the previous cases [ Fig.…”

Section: The Effects Of Thermal Reservoir Size and Boundarymentioning

confidence: 62%

Unification of nonequilibrium molecular dynamics and the mode-resolved phonon Boltzmann equation for thermal transport simulations

Feng

et al. 2020

Phys. Rev. B

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Nano-size confinement induces many intriguing non-Fourier heat conduction phenomena, such as nonlinear temperature gradients, temperature jumps near the contacts, and size-dependent thermal conductivity. Over the past decades, these effects have been studied and interpreted by nonequilibrium molecular dynamics (NEMD) and phonon Boltzmann transport equation (BTE) simulations separately, but no theory that unifies these two methods has ever been established. In this work, we unify these methods using a quantitative mode-level comparison and demonstrate that they are equivalent for various thermostats. We show that different thermostats result in different non-Fourier thermal transport characteristics due to the different mode-level phonon excitations inside the thermostats, which explains the different size-dependent thermal conductivities calculated using different reservoirs, even though they give the same bulk thermal conductivity. Specifically, the Langevin thermostat behaves like a thermalizing boundary in phonon BTE and provides mode-level thermal-equilibrium phonon outlets, while the Nose-Hoover chain thermostat and velocity rescaling method behave like biased reservoirs, which provide a spatially uniform heat generation and mode-level nonequilibrium phonon outlets. These findings explain why different experimental measurement methods can yield different size-dependent thermal conductivity. They also indicate that the thermal conductivity of materials can be tuned for various applications by specifically designing thermostats. The unification of NEMD and phonon BTE will largely facilitate the study of thermal transport in complex systems in the future by, e.g., replacing computationally unaffordable first-principles NEMD simulations with computationally less expensive spectral BTE simulations.

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Section: The Effects Of Thermal Reservoir Size and Boundarymentioning

confidence: 62%

Unification of nonequilibrium molecular dynamics and the mode-resolved phonon Boltzmann equation for thermal transport simulations

Feng

et al. 2020

Phys. Rev. B

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“…If all the atoms participate in the heat transfer, p 1. P can be calculated as (Yang et al, 2013;Shao et al, 2018;Han et al, 2019b):…”

Section: Phonon Participation Ratiomentioning

confidence: 99%

“…As one of the self-similar set, the Sierpinski carpet fractal (SCF) structure is introduced to construct the defective graphene (Kang et al, 2018;Han et al, 2019a;Han et al, 2020). The SCF defects in graphene can significantly increase the boundary scattering of phonon and thus significantly reduce the TC (Zhang et al, 2014;Wei et al, 2015;Shao et al, 2018). When the fractal level increases from 0 to 3, the TC of the SCF graphene monolayer decreases from 164.4 to 19.6 W/mK (Kang et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Investigation on Thermal Conductivity and Photon Behaviors of Graphene With Sierpinski Carpet Fractal Defects

Shao

et al. 2022

Front. Energy Res.

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The thermal conductivity (TC) of graphene with Sierpinski carpet fractal (SCF) and regular carpet (RC) defects is numerically studied by the non-equilibrium molecular dynamics (NEMD) method. The influences of porosity, fractal levels, and types of defects on the TC of graphene are clarified, and the underlying mechanisms of phonon behaviors are uncovered. The numerical results indicate that the defects in graphene induce the atoms that have the heat transfer blockage effect, and thus, the TC of defective graphene decreases with increasing porosity. With the increase in fractal levels, more atoms have the heat transfer blockage effect, which induces the TC of graphene with SCF defects to sharply decrease. Moreover, compared with the graphene with RC defects, more atoms participate in the heat transfer blockage under the graphene with SCF defects, which leads to the lower TC of graphene with SCF defects.

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“…The parameter σ represents the width of the phonon wave packet. The eigenvector and wavevector in equation (4) can be calculated by LD simulations using GULP [41]. To initialize phonon wave packet velocities, we calculate the initial velocity by ( )…”

Section: Phonon Wave Packet Simulationmentioning

confidence: 99%

Atomistic simulations of phonon behaviors in isotopically doped graphene with Sierpinski carpet fractal structure

Han

Fan

Wang

et al. 2020

Mater. Res. Express

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Two-dimensional (2D) graphene monolayer has been attached importance because of the fantastic physical properties. In this work, we conduct the atomistic simulations to evaluate the phonon behaviors in isotopically doped graphene with Sierpinski Carpet (SC) fractal structure. The thermal conductivities (k) with different fractal numbers are calculated by molecular dynamics simulation. The relationship between the k and the fractal number from 0 to 8 shows a first decreasing and then stable trend. The maximum reduction ratio of the k in SC fractal structures is 52.37%. Afterwards, we utilize the molecular dynamics simulation, phonon wave packet simulation and lattice dynamics simulation to investigate the phonon density of states (PDOS), energy transmission coefficient (ETC), phonon group velocity and participation ratio (PR) in SC fractal structures. In SC fractal structures, the PDOS increases in the low frequency region and the G-band will soften with the enhanced fractal number. We also observe that the isotopic doping atoms can lead to continuous reflected waves in SC fractal structure regions. Moreover, phonon modes in SC fractal structures possess the lower ETCs, phonon group velocities and PRs in comparison with the pristine graphene monolayer. Therefore, we attribute the lower k in SC fractal structures to the stronger phonon-impurity scattering and the increasing localized phonon modes.

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Understanding the mechanism of diffuse phonon scattering at disordered surfaces by atomistic wave-packet investigation

Cited by 40 publications

References 63 publications

Unification of nonequilibrium molecular dynamics and the mode-resolved phonon Boltzmann equation for thermal transport simulations

Unification of nonequilibrium molecular dynamics and the mode-resolved phonon Boltzmann equation for thermal transport simulations

Molecular Dynamics Investigation on Thermal Conductivity and Photon Behaviors of Graphene With Sierpinski Carpet Fractal Defects

Atomistic simulations of phonon behaviors in isotopically doped graphene with Sierpinski carpet fractal structure

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