An interfering Monte Carlo method for partially coherent phonon transport in superlattices

2017 ◽  
Vol 107 ◽  
pp. 534-543 ◽  
Author(s):  
Qi Li ◽  
Wenjing Ye
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Phonon Transport ◽  
Coherent Phonon ◽  
Partially Coherent

Thermal Rectification by Ballistic Phonons in Asymmetric Nanostructures

2009 ◽  
Author(s):  
John Miller ◽  
Wanyoung Jang ◽  
Chris Dames
Keyword(s):  
Monte Carlo ◽  
Distribution Function ◽  
Monte Carlo Method ◽  
Phonon Transport ◽  
Reverse Direction ◽  
Careful Attention ◽  
Energy Carriers ◽  
Thermal Rectification ◽  
Special Surface ◽  
Ballistic Phonons

In analogy to an electrical diode, a thermal rectifier transports heat more easily in one direction than in the reverse direction. Among various possible nanoscale rectification mechanisms, a ballistic rectifier relies on asymmetric scattering of energy carriers, as has been suggested for phonon transport in a sawtooth nanowire [S. Saha, L. Shi, & R. Prasher, IMECE 2006] or nanowire with special surface specularity function [N.A. Roberts and D.G. Walker, ITherm 2008]. We have used a Landauer-Buttiker method as well as a Monte Carlo method to model the asymmetric heat transport in such nanostructures, with careful attention to boundary conditions that satisfy the 2nd Law of Thermodynamics. The calculations show that ballistic rectification is only significant at relatively large “thermal bias,” which causes significant anisotropy in the distribution function of energy carriers emitted at each of the two thermal contacts. We also propose experiments to observe this phenomenon using either phonons or photons.

Monte Carlo Simulation of Steady-State Microscale Phonon Heat Transport

2008 ◽  
Vol 130 (7) ◽  
Author(s):  
Jaona Randrianalisoa ◽  
Dominique Baillis
Keyword(s):  
Heat Transfer ◽  
Thin Films ◽  
Monte Carlo ◽  
Heat Conduction ◽  
Steady State ◽  
Monte Carlo Method ◽  
Silicon Nanowires ◽  
Silicon Film ◽  
Relaxation Times ◽  
Phonon Transport

Heat conduction in submicron crystalline materials can be well modeled by the Boltzmann transport equation (BTE). The Monte Carlo method is effective in computing the solution of the BTE. These past years, transient Monte Carlo simulations have been developed, but they are generally memory demanding. This paper presents an alternative Monte Carlo method for analyzing heat conduction in such materials. The numerical scheme is derived from past Monte Carlo algorithms for steady-state radiative heat transfer and enables us to understand well the steady-state nature of phonon transport. Moreover, this algorithm is not memory demanding and uses very few iteration to achieve convergence. It could be computationally more advantageous than transient Monte Carlo approaches in certain cases. Similar to the famous Mazumder and Majumdar’s transient algorithm (2001, “Monte Carlo Study of Phonon Transport in Solid Thin Films Including Dispersion and Polarization,” ASME J. Heat Transfer, 123, pp. 749–759), the dual polarizations of phonon propagation, the nonlinear dispersion relationships, the transition between the two polarization branches, and the nongray treatment of phonon relaxation times are accounted for. Scatterings by different mechanisms are treated individually, and the creation and/or destruction of phonons due to scattering is implicitly taken into account. The proposed method successfully predicts exact solutions of phonon transport across a gallium arsenide film in the ballistic regime and that across a silicon film in the diffusion regime. Its capability to model the phonon scattering by boundaries and impurities on the phonon transport has been verified. The current simulations agree well with the previous predictions and the measurement of thermal conductivity along silicon thin films and along silicon nanowires of widths greater than 22nm. This study confirms that the dispersion curves and relaxation times of bulk silicon are not appropriate to model phonon propagation along silicon nanowires of 22nm width.

scholarly journals Deviational Phonons and Thermal Transport at the Nanoscale

2012 ◽  
Author(s):  
Jean-Philippe M. Péraud ◽  
Nicolas G. Hadjiconstantinou
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Three Dimensional ◽  
Simulation Method ◽  
Phonon Transport ◽  
Statistical Uncertainty ◽  
Small Temperature ◽  
Efficient Simulation ◽  
Transport Problems ◽  
Individual Particles

We present a new method for simulating phonon transport at the nanoscale. The proposed approach is based on the recently developed energy-based deviational Monte Carlo method by the authors [Phys. Rev. B 84, 205331, 2011] which achieves significantly reduced statistical uncertainty compared to standard Monte Carlo methods by simulating only the deviation from equilibrium. Here, we show that under linearized conditions (small temperature differences) the trajectories of individual particles simulating the deviation from equilibrium can be decoupled and can thus be simulated independently, without introducing any additional approximation. This leads to a particularly simple and efficient simulation method that can be used to treat steady and transient phonon transport problems in arbitrary three-dimensional geometries.

Partially coherent phonon transport in two-dimensionally rough nanowires

2012 ◽  
Vol 11 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Jyothi Sadhu ◽  
Myunghoon Seong ◽  
Sanjiv Sinha
Keyword(s):  
Phonon Transport ◽  
Coherent Phonon ◽  
Partially Coherent

Individual Phonon Branch Contribution to Thermal Conductivity of 3C-SiC Using the Monte Carlo Method

2018 ◽  
Author(s):  
Arden N. Barnes ◽  
Nick Roberts
Keyword(s):  
Thermal Conductivity ◽  
Monte Carlo ◽  
Monte Carlo Method ◽  
High Strength ◽  
Longitudinal Optical ◽  
Phonon Transport ◽  
The Monte Carlo Method ◽  
Transverse Acoustic ◽  
Individual Contributions ◽  
The Individual

Silicon carbide (SiC) is a useful semiconductor material due to its high thermal conductivity (λ), low reactivity, and high strength. These properties also make it an ideal nuclear fuel cladding material. Because heat transfer in SiC is dominated by phonons, there is value in understanding how different phonon branches contribute to λ. To accomplish this, it is useful to run simulations which employ fewer phonon branches than normally exist. In materials where phonons dominate heat transport, such as SiC, the Monte Carlo method as applied to phonon transport is suitable for estimating λ. This work uses the Monte Carlo method to estimate λ of 3C-SiC using four phonon branches, namely, transverse acoustic (TA), longitudinal acoustic (LA), transverse optical (TO), and longitudinal optical (LO). By adding branches into the simulation and measuring λ, the individual contributions to λ from each branch can be determined.

MFP-Based Monte Carlo Method for Nanostructure Phonon Transport

2019 ◽  
Author(s):  
Jincai Yu ◽  
Wenjing Ye ◽  
Baoling Huang ◽  
Daniel Josephus Villaroman ◽  
Qi Wang
Keyword(s):  
Thermal Conductivity ◽  
Monte Carlo ◽  
Monte Carlo Method ◽  
Large Scale ◽  
Variance Reduction ◽  
Computational Cost ◽  
Phonon Transport ◽  
First Principles Calculation ◽  
Nanostructured Systems ◽  
Very High

Abstract Phonon Monte Carlo method is a popular method for modeling particle dominated phonon transport. Its accuracy critically depends on its inputs such as relaxation time and dispersion, which are difficult to be obtained accurately and efficiently. As a result, empirical models with many fitting parameters are often used. In addition, for large-scale 3D nanostructured systems, the required computational cost is very high. In this article, we present an efficient and highly parallelizable phonon Monte Carlo method using MFP-cumulative thermal conductivity as the only input. The efficiency is enhanced by incorporating the recently proposed variance-reduction method, and the accuracy is ensured because the MFP-based cumulative thermal conductivity can be accurately obtained by experiments or first principles calculation. Moreover, with the MEP-cumulative thermal conductivity as the input, optical phonons can be naturally included in the calculation, which further improves the accuracy.

Outbursts of comet Schwassmann-Wachmann 1, and the cloud of interplanetary boulders

1974 ◽  
Vol 22 ◽  
pp. 307 ◽  
Author(s):  
Zdenek Sekanina
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Interplanetary Space ◽  
Porous Matrix ◽  
Maximum Diameter ◽  
Expansion Velocity ◽  
Solid Constituent ◽  
Meteoric Material ◽  
Periodic Comet

AbstractIt is suggested that the outbursts of Periodic Comet Schwassmann-Wachmann 1 are triggered by impacts of interplanetary boulders on the surface of the comet’s nucleus. The existence of a cloud of such boulders in interplanetary space was predicted by Harwit (1967). We have used the hypothesis to calculate the characteristics of the outbursts – such as their mean rate, optically important dimensions of ejected debris, expansion velocity of the ejecta, maximum diameter of the expanding cloud before it fades out, and the magnitude of the accompanying orbital impulse – and found them reasonably consistent with observations, if the solid constituent of the comet is assumed in the form of a porous matrix of lowstrength meteoric material. A Monte Carlo method was applied to simulate the distributions of impacts, their directions and impact velocities.

Structures and crystallization of vacuum-deposited amorphous Se and Sb films

1990 ◽  
Vol 48 (4) ◽  
pp. 140-141
Author(s):  
Makoto Shiojiri ◽  
Toshiyuki Isshiki ◽  
Tetsuya Fudaba ◽  
Yoshihiro Hirota
Keyword(s):  
Monte Carlo ◽  
Electron Microscope ◽  
Monte Carlo Method ◽  
Computer Program ◽  
Radial Distribution ◽  
Film Formation ◽  
Amorphous State ◽  
Two Dimensional ◽  
Amorphous Films ◽  
Binding Condition

In hexagonal Se crystal each atom is covalently bound to two others to form an endless spiral chain, and in Sb crystal each atom to three others to form an extended puckered sheet. Such chains and sheets may be regarded as one- and two- dimensional molecules, respectively. In this paper we investigate the structures in amorphous state of these elements and the crystallization.HRTEM and ED images of vacuum-deposited amorphous Se and Sb films were taken with a JEM-200CX electron microscope (Cs=1.2 mm). The structure models of amorphous films were constructed on a computer by Monte Carlo method. Generated atoms were subsequently deposited on a space of 2 nm×2 nm as they fulfiled the binding condition, to form a film 5 nm thick (Fig. 1a-1c). An improvement on a previous computer program has been made as to realize the actual film formation. Radial distribution fuction (RDF) curves, ED intensities and HRTEM images for the constructed structure models were calculated, and compared with the observed ones.

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