Controlling Thermal Conductivity of Alloys via Atomic Ordering

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
John C. Duda ◽  
Timothy S. English ◽  
Donald A. Jordan ◽  
Pamela M. Norris ◽  
William A. Soffa
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Nonequilibrium Molecular Dynamics ◽  
Melt Temperature ◽  
Lennard Jones ◽  
Thermodynamic Conditions ◽  
Order Of Magnitude ◽  
Fixed Composition ◽  
Dynamics Simulations

Many random substitutional solid solutions (alloys) will display a tendency to atomically order given the appropriate kinetic and thermodynamic conditions. Such order–disorder transitions will result in major crystallographic reconfigurations, where the atomic basis, symmetry, and periodicity of the alloy change dramatically. Consequently, phonon behavior in these alloys will vary greatly depending on the type and degree of ordering achieved. To investigate these phenomena, the role of the order–disorder transition on phononic transport properties of Lennard–Jones type binary alloys is explored via nonequilibrium molecular dynamics simulations. Particular attention is paid to regimes in which the alloy is only partially ordered. It is shown that by varying the degree of ordering, the thermal conductivity of a binary alloy of fixed composition can be tuned across an order of magnitude at 10% of the melt temperature, and by a factor of three at 40% of the melt temperature.

Role of Chemical Ordering on Phononic Transport in Binary Alloys

2011 ◽  
Author(s):  
John C. Duda ◽  
Timothy S. English ◽  
William A. Soffa ◽  
Donald A. Jordan ◽  
Pamela M. Norris
Keyword(s):  
Order Parameter ◽  
Binary Alloys ◽  
Range Order Parameter ◽  
Lennard Jones ◽  
Chemical Ordering ◽  
Thermodynamic Conditions ◽  
Order Of Magnitude ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations

Many random substitutional solid solutions (alloys) will display a tendency to chemically order given the appropriate kinetic and thermodynamic conditions. Such order-disorder transitions will result in major crystallographic reconfigurations, where the atomic basis, symmetry, and periodicity of the alloy change dramatically. Consequently, phonon behavior in these alloys will vary greatly depending on the type and degree of ordering achieved. To investigate these phenomena, the role of the order-disorder transition on phononic transport properties of Lennard-Jones type binary alloys is explored via non-equilibrium molecular dynamics simulations. Particular attention is paid to regimes in which the alloy is only partially ordered. It is shown that, through exploitation of the long-range order parameter, thermal conductivity of binary alloys can be effectively tuned across half an order of magnitude at low-to-moderate temperatures.

An Atomistic Simulation Study of the Role of Asperities and Indentations on Heterogeneous Bubble Nucleation

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Brian R. Novak ◽  
Edward J. Maginn ◽  
Mark J. McCready
Keyword(s):  
Heat Flux ◽  
Atomistic Simulation ◽  
Surface Defects ◽  
Constant Heat Flux ◽  
Bubble Nucleation ◽  
Nonequilibrium Molecular Dynamics ◽  
Lennard Jones ◽  
Dynamics Simulations ◽  
Fluid Interaction

Heterogeneous bubble nucleation was studied on surfaces having nanometer scale asperities and indentations as well as different surface-fluid interaction energies. Nonequilibrium molecular dynamics simulations at constant normal stress and either temperature or heat flux were carried out for the Lennard–Jones fluid in contact with a Lennard–Jones solid. When surface defects were of the same size or smaller than the estimated critical nucleus (the smallest nucleus whose growth is energetically favored) size of 1000–2000Å3, there was no difference between the defected surfaces and atomically smooth surfaces. On the other hand, surfaces with significantly larger indentations had nucleation rates that were about two orders of magnitude higher than the systems with small defects. Moreover, nucleation was localized in the large indentations. This localization was greatest under constant heat flux conditions and when the solid-fluid interactions were weak. The results suggest strategies for enhancing heterogeneous bubble nucleation rates as well as for controlling the location of nucleation events.

An Investigation on Thermal Conductivity of Fluid in a Nanochannel by Nonequilibrium Molecular Dynamics Simulations

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Mohammad Bagheri Motlagh ◽  
Mohammad Kalteh
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Poiseuille Flow ◽  
Driving Force ◽  
Dynamics Simulation ◽  
Nonequilibrium Molecular Dynamics ◽  
Wall Roughness ◽  
Dynamics Simulations ◽  
Effect Of Copper

Abstract In this paper, molecular dynamics simulation is used to investigate the effect of copper and argon nanochannels size on the thermal conductivity of argon. Thermal conductivity is calculated by nonequilibrium molecular dynamics (NEMD) simulation. Simulations are performed for different distances between the walls. Results for both copper and argon walls are investigated individually. Results show that the existence of argon walls has little effect on the thermal conductivity. However, the amount of it for the argon confined between the copper walls is affected by the distance between the two walls. In the same way, the effect of wall roughness on the thermal conductivity is investigated, which shows that roughness is effective only for low distances between the walls. Also, the thermal conductivity of argon under Poiseuille flow in a nanochannel is studied. The results indicate that by increasing the driving force, the thermal conductivity increases and the increase ratio is higher for larger forces.

Thermal Conductivity of Amorphous and Crystalline SiO2 Nano-Films from Molecular Dynamics Simulations

2012 ◽  
Vol 501 ◽  
pp. 64-69 ◽  
Author(s):  
Yan He ◽  
Yuan Zheng Tang ◽  
Man Ding ◽  
Lian Xiang Ma
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Film Thickness ◽  
Molecular Dynamics Simulations ◽  
Grain Morphology ◽  
Nonequilibrium Molecular Dynamics ◽  
Calculated Temperature ◽  
Dynamics Simulations ◽  
Different Thickness ◽  
Good Agreement

Normal thermal conductivity of amorphous and crystalline SiO2nano-films is calculated by nonequilibrium molecular dynamics (NEMD) simulations in the temperature range from 100 to 700K and thicknesses from 2 to 6nm. The calculated temperature and thickness dependences of thermal conductivity are in good agreement with previous literatures. In the same thickness, higher thermal conductivity is obtained for crystalline SiO2nano-films. And more importantly, for amorphous SiO2nano-films, thickness can be any direction of x, y, z-axis without effect on the normal thermal conductivity, for crystalline SiO2nano-films, the different thickness directions obtain different thermal conductivity results. The different results of amorphous and crystalline SiO2nano-films simply show that film thickness and grain morphology will cause different effects on thermal conductivity.

Superlattice Analysis for Tailored Thermal Transport Characteristics

2006 ◽  
Author(s):  
E. S. Landry ◽  
A. J. H. McGaughey ◽  
M. I. Hussein
Keyword(s):  
Thermal Conductivity ◽  
Thermal Transport ◽  
Direct Method ◽  
Continuum Theory ◽  
Lennard Jones ◽  
Constituent Species ◽  
The Cross ◽  
Dynamics Simulations ◽  
Superlattice Period

Molecular dynamics simulations and the Green-Kubo method are used to predict the thermal conductivity of binary Lennard-Jones superlattices and alloys. The superlattice thermal conductivity trends are in agreement with those obtained through the direct method, verifying that the Green-Kubo method can be used to examine thermal transport in heterostructures. The simulation temperature and the constituent species are fixed while the superlattice period structure is varied with the goals of (i) minimizing the cross-plane thermal conductivity and (ii) maximizing the ratio of in-plane to cross-plane thermal conductivities. The superlattice thermal conductivity in both the cross-plane and in-plane directions is found to be greater than the corresponding alloy value and less than the value predicted from continuum theory. The anisotropy of the thermal conductivity tensor is found to be at a maximum for a superlattice with a uniform layer thickness. Lattice dynamics calculations are used to investigate the role of optical phonons in the thermal transport.

Thermal Conductivity of Graphene on Nanostructure Size from Nonequilibrium Molecular Dynamics Simulations

2020 ◽  
Vol 17 (4) ◽  
pp. 1566-1570
Author(s):  
Xianqi Wei ◽  
Zelin Li ◽  
Junchen Lu ◽  
Shunlong Xu ◽  
Yuancheng Zhu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Thermal Management ◽  
Strong Dependence ◽  
Thermal Conductance ◽  
Mean Free Path ◽  
Dynamics Simulation ◽  
Nonequilibrium Molecular Dynamics ◽  
Edge Type ◽  
Dynamics Simulations

Thermal transport of graphene occupies a unique place in thermal management of electronic devices, especially for nanosize devices with high-density integration and high dissipated power. The structure of graphene on nanometer scale changes its thermal conductance. Here, the thermal characters of graphene have been researched by nonequilibrium molecular dynamics simulation (NEMDS) at room temperature. Special attention is focused on the edge type (zigzag or armchair) and nanostructure size dependence of conductivity for heat. The consequences suggest that the thermal conductivity of zigzag edge has been higher than that of armchair, which is because of the higher phonon group velocities. Furthermore, thermal conductivity shows a rising tendency, when the model is calculated from length of 21.84 nm to 43.78 nm. The result indicates that the thermal property performs a strong dependence on nanostructure size which is less than phonon mean free path (775 nm). Our research highlights the significance of structure attribute relationships together with providing useful guideline in calculations for nanosize devices thermal management.

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.

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