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.

Thermal Conductivity of Hexagonal SiC Nanowire by Nonequilibrium Molecular Dynamics Simulations

2014 ◽  
Vol 487 ◽  
pp. 102-105
Author(s):  
Zan Wang ◽  
Hua Wei Guan ◽  
Ke Dong Bi
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Free Path ◽  
Density Functional ◽  
Mean Free Path ◽  
Nonequilibrium Molecular Dynamics ◽  
Functional Theory ◽  
Sic Nanowires ◽  
Dynamics Simulations ◽  
Dynamics Method

Using nonequilibrium Molecular Dynamics method, thermal properties of hexagonal 4H-SiC and 6H-SiC nanowires are investigated. The quantum errors between realistic temperatures and Molecular dynamics temperatures are rectified based on Density Functional Theory. Thermal conductivities of 4H-SiC and 6H-SiC nanowires are both simulated from 50K to 800K. The scale effect on the thermal conductivity of nanowire is also investigated by varying the nanowires length from 10nm to 130nm. Results indicate, if the length of phonon mean free path is shorter than that of nanowire, phonon-surface scattering will surpass boundary scattering to contribute thermal resistances. Therefore, the thermal conductivity of 4H-SiC or 6H-SiC nanowire is mainly determined by the comparability between the length of nanowires and phonon mean free path.

Molecular Dynamics Simulations and Kapitza Conductance Prediction of Si/Au Systems Using the New Full 2NN MEAM Si/Au Cross-Potential

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Carolina Abs da Cruz ◽  
Patrice Chantrenne ◽  
Xavier Kleber
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Physical Vapor Deposition ◽  
Local Density ◽  
Mean Free Path ◽  
Nonequilibrium Molecular Dynamics ◽  
Kapitza Conductance ◽  
Dynamics Simulations ◽  
Good Agreement

Superlattices made by superposing dielectric and metal nanolayers are of great interest as their small size restricts the thermal energy carrier mean free path, decreasing the thermal conductivity and thereby increasing the thermoelectric figure of merit. It is, therefore, essential to predict their thermal conductivity. Potentials for Au and Si are discussed, and the potential of second nearest-neighbor modified embedded atom method (2NN MEAM) is chosen as being the best for simulating heat transfer in Si/Au systems. Full 2NN MEAM Si/Au cross-potential parameterization is developed, and the results are compared with ab initio calculations to test its ability to reproduce local density approximation (LDA) calculations. Volume-constant (NVT) molecular dynamics simulations are performed to deposit Au atoms on an Si substrate by physical vapor deposition, and the results of the intermixing zone are in good agreement with the Cahn and Hilliard theory. Nonequilibrium molecular dynamics simulations are performed for an average temperature of 300 K to determine the Kapitza conductance of Si/Au systems, and the obtained value of 158 MW/m 2 K is in good agreement with the results of Komarov et al. for Au deposited on isotopically pure Si- 28 and natural Si, with values ranging between 133 and 182 MW/m2 K.

A Molecular Dynamics Study of Thermal Conductivity in Nanocomposites via the Phonon Wave Packet Method

2009 ◽  
Author(s):  
Zhiting Tian ◽  
Sang Kim ◽  
Ying Sun ◽  
Bruce White
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Wave Packet ◽  
Molecular Dynamics Simulations ◽  
Phonon Scattering ◽  
Flow Direction ◽  
Normal Incidence ◽  
Material Interfaces ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations

The phonon wave packet technique is used in conjunction with the molecular dynamics simulations to directly observe phonon scattering at material interfaces. The phonon transmission coefficient of nanocomposites is examined as a function of the defect size, thin film thickness, orientation of interface to the heat flow direction. To generalize the results based on phonons in a narrow frequency range and at normal incidence, the effective thermal conductivity of the same nanocomposite structure is calculated using non-equilibrium molecular dynamics simulations for model nanocomposites formed by two mass-mismatched Ar-like solids and heterogeneous Si-SiCO2 systems. The results are compared with the modified effective medium formulation for nanocomposites.

Experiments on the flow of heat in liquid helium below 0.7 °K

1958 ◽  
Vol 246 (1246) ◽  
pp. 390-405 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Liquid Helium ◽  
Free Path ◽  
Empirical Relation ◽  
Mean Free Path ◽  
Series Of Experiments ◽  
The Mean ◽  
Set Up ◽  
Low Pressures ◽  
Measured Thermal Conductivity

A series of experiments has been performed to study the steady flow of heat in liquid helium in tubes of diameter 0.05 to 1.0 cm at temperatures between 0.25 and 0.7 °K. The results are interpreted in terms of the flow of a gas of phonons, in which the mean free path λ varies with temperature, and may be either greater or less than the diameter of the tube d . When λ ≫ d the flow is limited by the scattering of the phonons at the walls, and the effect of the surface has been studied, but when λ ≪ d viscous flow is set up in which the measured thermal conductivity is increased above that for wall scattering. This behaviour is very similar to that observed in the flow of gases at low pressures, and by applying kinetic theory to the problem it can be shown that the mean free path of the phonons characterizing viscosity can be expressed by the empirical relation λ = 3.8 x 10 -3 T -4.3 cm. This result is inconsistent with the temperature dependence of λ as T -9 predicted theoretically by Landau & Khalatnikov (1949).

Thermal Conductivity in Thin Silicon Nanowires with Rough Surfaces by Molecular Dynamics Simulations

2010 ◽  
Author(s):  
Xueming Yang ◽  
Albert C. To ◽  
Jane W. Z. Lu ◽  
Andrew Y. T. Leung ◽  
Vai Pan Iu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Silicon Nanowires ◽  
Rough Surfaces ◽  
Thin Silicon ◽  
Dynamics Simulations

Multiscale Simulations of Thermoelectric Properties of PBTE

2008 ◽  
Author(s):  
Bo Qiu ◽  
Hua Bao ◽  
Xiulin Ruan
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Thermoelectric Properties ◽  
Transport Coefficients ◽  
Multiscale Simulation ◽  
Full Potential ◽  
Boltzmann Transport ◽  
Pair Potentials ◽  
Dynamics Simulations

In this paper, thermoelectric properties of bulk PbTe are calculated using first principles calculations and molecular dynamics simulations. The Full Potential Linearized Augmented Plane Wave (FP-LAPW) method is first employed to calculate the PbTe band structure. The transport coefficients (Seebeck coefficient, electrical conductivity, and electron thermal conductivity) are then computed using Boltzmann transport equation (BTE) under the constant relaxation time approximation. Interatomic pair potentials in the Buckingham form are also derived using ab initio effective charges and total energy data. The effective interatomic pair potentials give excellent results on equilibrium lattice parameters and elastic constants for PbTe. The lattice thermal conductivity of PbTe is then calculated using molecular dynamics simulations with the Green-Kubo method. In the end, the figure of merit of PbTe is computed revealing the thermoelectric capability of this material, and the multiscale simulation approach is shown to have the potential to identify novel thermoelectric materials.

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