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.

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.

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.

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.

Molecular Dynamics Study of the Elastic Response of Crystalline, Amorphous and Chemically Disordered NiZr2

1990 ◽  
Vol 205 ◽  
Author(s):  
Carlo Massobrio ◽  
Vittorio Rosato ◽  
Francois Willaime
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Elastic Constants ◽  
Order Parameter ◽  
Elastic Response ◽  
Range Order Parameter ◽  
Long Range Order ◽  
Amorphous Phases ◽  
Antisite Defects ◽  
Dynamics Simulations

AbstractWe calculate the shear elastic constants of the alloy NiZr2 by molecular dynamics simulations in the crystalline and amorphous phases as well as upon introduction of antisite defects in the crystal at T=300K. For S (long range order parameter) equal to 0.5, the system is amorphous and C' is larger than the same quantity relative to the crystal whereas C44 and C66 are smaller.

Molecular Dynamics Computations of Flow in Constricted and Wavy Nano Channels

2009 ◽  
Author(s):  
D. D. Marsh ◽  
S. P. Vanka ◽  
I. M. Jasiuk ◽  
M. L. Knothe Tate
Keyword(s):  
Molecular Dynamics ◽  
Boundary Conditions ◽  
Particle Interactions ◽  
Pressure Drops ◽  
Lennard Jones ◽  
Depth Direction ◽  
Depth Dimension ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
Stochastic Boundary

This paper explores flow in complex nano-sized channels by use of molecular dynamics. Due to the small nature of these channels and to better capture wall effects, non-equilibrium molecular dynamics simulations were performed. Straight, constricted and sawtooth channels were studied. The function used for modeling the particle interactions is the Lennard-Jones 6–12 potential. Stochastic boundary conditions are used in conjunction with periodic boundary conditions in a 3D domain. Computational enhancements including cell subdivision and neighbor listing provide increased efficiency. The channels were homogeneous in the depth dimension and the results were averaged in the depth direction in order to improve averages. Velocity profiles at several locations were computed and are presented in the paper. The eventual goal of this research is to study the effects of time-dependent inflow and pressure drops so as to understand the flow in nano channels in the human bone.

scholarly journals Thermal and Caloric Properties of Fluids from Non-equilibrium Molecular Dynamics Simulations using the Two-gradient Method

2021 ◽  
Author(s):  
Martin P. Lautenschläger ◽  
Hans Hasse
Keyword(s):  
Molecular Dynamics ◽  
Heat Capacity ◽  
Thermal Expansion ◽  
Molecular Dynamics Simulations ◽  
Transport Properties ◽  
Thermal Expansion Coefficient ◽  
Gradient Method ◽  
Lennard Jones ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations

Transport properties of fluids can be determined efficiently from non-equilibrium molecular dynamics simulations using the two-gradient method which was introduced recently. It is shown here that also thermal and caloric properties of fluids can be determined accurately and efficiently along with the transport properties using this method. In a single run, all these properties are obtained for a series of state points at different temperatures and constant pressure. The truncated and shifted Lennard-Jones (LJTS) fluid is studied here as a test case. Data are reported for about 700 state points in the range of (T = [0:7; 8:5] and ? = [0:2; 1:0]). Besides data on the thermal conductivity, shear viscosity, and selfdiffusion the following thermal and caloric properties were measured: pressure p, internal energy u, enthalpy h, isobaric heat capacity cp and thermal expansion coefficient ?p. The results of the thermal and caloric properties agree very well with those from an accurate equation of state from the literature. Also the shear rate dependence of these properties can be studied easily with the two-gradient method. Keywords: local equilibrium; Lennard-Jones fluid; isobaric heat capacity; thermal expansion coefficient

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