scholarly journals Frequency-dependent phonon mean free path in carbon nanotubes from nonequilibrium molecular dynamics

2015 ◽  
Vol 91 (11) ◽  
Author(s):  
K. Sääskilahti ◽  
J. Oksanen ◽  
S. Volz ◽  
J. Tulkki
Keyword(s):  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Free Path ◽  
Mean Free Path ◽  
Nonequilibrium Molecular Dynamics ◽  
Frequency Dependent

scholarly journals The Thermal Conductivity of Carbon Nanotubes with Defects and Intramolecular Junctions

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Qiaoli Zhou ◽  
Fanyan Meng ◽  
Zhuhong Liu ◽  
Sanqiang Shi
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Temperature Gradient ◽  
Temperature Profile ◽  
Free Path ◽  
Mean Free Path ◽  
Nonequilibrium Molecular Dynamics ◽  
Large Temperature ◽  
Large Temperature Gradient

The thermal conductivity of various carbon nanotubes with defects or intramolecular junctions was studied using nonequilibrium molecular dynamics approach. The results show that the thermal conductivity of both armchair and zigzag carbon nanotubes increased with the decrease of the radius of the tube. The thermal conductivity of armchair tube is higher than that of zigzag tube when the radii of the two tubes are kept almost same. Discontinuities appear on the temperature profile along the tube axial at the region of IMJ, resulting in the large temperature gradient and thus lower thermal conductivity of(n,n)/(m,0)tube with one IMJ and(m,0)/(n,n)/(m,0)tube with two IMJs. For the(m,0)/(n,n)/(m,0)tube with two IMJs, phonon mean free path of the middle(n,n)tube is much smaller than that of the isolate(n,n)tube.

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.

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.

scholarly journals Electronic mean free path in as-produced and purified single-wall carbon nanotubes

2005 ◽  
Vol 86 (12) ◽  
pp. 122106 ◽  
Author(s):  
H. Kajiura ◽  
A. Nandyala ◽  
U. C. Coskun ◽  
A. Bezryadin ◽  
M. Shiraishi ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Free Path ◽  
Mean Free Path ◽  
Single Wall Carbon Nanotubes ◽  
Single Wall Carbon

scholarly journals Enhancement of Interfacial Thermal Conductance of SiC by Overlapped Carbon Nanotubes and Intertube Atoms

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Chengcheng Deng ◽  
Xiaoxiang Yu ◽  
Xiaoming Huang ◽  
Nuo Yang
Keyword(s):  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Silicon Carbide ◽  
Density Of States ◽  
Probability Distributions ◽  
Thermal Conductance ◽  
Nonequilibrium Molecular Dynamics ◽  
Vibrational Density Of States ◽  
Interfacial Thermal Conductance ◽  
Vibrational Density

A new way was proposed to enhance the interfacial thermal conductance (ITC) of silicon carbide (SiC) composite through the overlapped carbon nanotubes (CNTs) and intertube atoms. By nonequilibrium molecular dynamics (NEMD) simulations, the dependence of ITC on both the number of intertube atoms and the temperature was studied. It is indicated that the ITC can be significantly enhanced by adding intertube atoms and finally becomes saturated with the increase of the number of intertube atoms. And the mechanism is discussed by analyzing the probability distributions of atomic forces and vibrational density of states (VDOS). This work may provide some guidance on enhancing the ITC of CNT-based composites.

scholarly journals Investigating the Effect of Solid Boundaries on the Gas Molecular Mean-Free-Path

2009 ◽  
Author(s):  
Erik J. Arlemark ◽  
Jason M. Reese
Keyword(s):  
Molecular Dynamics ◽  
Boundary Conditions ◽  
Free Path ◽  
Mean Free Path ◽  
Gas Flows ◽  
Standard Temperature ◽  
Binary Collisions ◽  
The Mean ◽  
Temperature And Pressure ◽  
Definition Of

A key parameter for micro-gas-flows, the mean free path, is investigated in this paper. The mean free path is used in various models for predicting micro gas flows, both in the governing equations and their boundary conditions. The conventional definition of the mean free path is based on the assumption that only binary collisions occur and is commonly described using the macroscopic quantities density, viscosity and temperature. In this paper we compare the prediction by this definition of the mean free paths for helium, neon and argon gases under standard temperature and pressure conditions, with the mean free paths achieved by measurements of individual molecules using the numerical simulation technique of molecular dynamics. Our simulation using molecular dynamics consists of a cube with six periodic boundary conditions, allowing us to simulate an unconfined gas “package”. Although, the size of this package is important, since its impact on computational cost is considerable, it is also important to have enough simulated molecules to average data from. We find that the molecular dynamics method using 20520 simulated molecules yields results that are within 1% accuracy from the conventional definition of the mean free paths for neon and argon and within 2.5% for helium. We can also conclude that the normal approximation of only considering binary collisions is seemingly adequate for these gases under standard temperature and pressure conditions. We introduce a single planar wall and two parallel planar walls to the simulated gas of neon and record the mean free paths at various distances to the walls. It is found that the mean free paths affected by molecular collisions with the walls corresponds well with theoretical models up to Knudsen numbers of 0.2.

Thermal properties of pillared-graphene nanostructures

2015 ◽  
Vol 1727 ◽  
Author(s):  
M. Rifu ◽  
K. Shintani
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Thermal Properties ◽  
Molecular Dynamics Simulation ◽  
Dynamics Simulation ◽  
Nonequilibrium Molecular Dynamics ◽  
Nonequilibrium Molecular Dynamics Simulation ◽  
Thermal Conductivities ◽  
Graphene Nanostructures

ABSTRACTThe thermal conductivities of pillared-graphene nanostructures (PGNSs) are obtained using nonequilibrium molecular-dynamics simulation. It is revealed their thermal conductivities are much smaller than the thermal conductivities of carbon nanotubes (CNTs). This fact is explained by examining the density of states (DOS) of the local phonons of PGNSs. It is also found the thermal conductivity of a PGNS linearly decreases with the increase of the inter-pillar distance.

1017 Molecular Dynamics Study on Mean Free Path

2005 ◽  
Vol 2005.42 (0) ◽  
pp. 343-344
Author(s):  
Masayoshi URADE ◽  
Toshihiro IWAKI
Keyword(s):  
Molecular Dynamics ◽  
Free Path ◽  
Mean Free Path
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