Multiscale Simulations of Anisotropic Grain Growth Using Wavelet Based Multiresolution Analysis

2016 ◽  
Vol 83 (10) ◽  
Author(s):  
J. B. Allen
Keyword(s):  
Molecular Dynamics ◽  
Monte Carlo ◽  
Grain Boundary ◽  
Molecular Dynamics Simulations ◽  
Grain Growth ◽  
Multiresolution Analysis ◽  
Wavelet Transforms ◽  
Multiscale Simulation ◽  
Inherent Anisotropy ◽  
Dynamics Simulations

The present work serves to document the development and findings associated with a wavelet-based multiscale simulation analysis for anisotropic grain growth of a two-dimensional polycrystalline material. In particular, lattice-based Monte Carlo and atomically-based Molecular Dynamics simulations are used to compute the grain boundary energies over their respective spatial domains. Serial coupling is performed utilizing an orthonormal set of Haar wavelet transforms embedded within a corresponding multiresolution analysis. For the Monte Carlo approach, anisotropies in grain boundary energies, caused by differences in grain orientation (texturing), are examined using two distinct methods, while the molecular dynamics simulations, offering inherent anisotropy, are conducted assuming the interatomic Lennard Jones potential. Among other findings, under the present context, the results confirm the viability of the wavelet-based multiresolution analysis (MRA) method for use as a potential coupling agent, and provide substantiation for its use with other applications. The results further offer quantitative comparisons between isotropic and anisotropic modeling results, and demonstrate their range of applicability.

Grain Growth Stagnation Caused by the Grain Boundary Roughening Transition

2012 ◽  
Vol 715-716 ◽  
pp. 415-415
Author(s):  
Elizabeth A. Holm ◽  
Stephen M. Foiles
Keyword(s):  
Molecular Dynamics ◽  
Transition Temperature ◽  
Grain Boundary ◽  
Molecular Dynamics Simulations ◽  
Grain Growth ◽  
Boundary Mobility ◽  
Grain Boundary Mobility ◽  
Annealing Temperatures ◽  
Roughening Transition ◽  
Dynamics Simulations

Molecular dynamics simulations of bicrystals show that grain boundaries undergo a thermal roughening transition, and the grain boundary mobility increases abruptly when the boundary roughens. The roughening transition temperature varies widely from boundary to boundary, ranging from less than 0.4 to more than 0.9 of the melting temperature. Thus, at typical annealing temperatures we expect polycrystals to contain both smooth (slow) and rough (fast) boundaries, with the fraction of each type varying with temperature.

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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