Recent progress in the concurrent atomistic-continuum method and its application in phonon transport
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Recent progress in the concurrent atomistic-continuum method and its application in phonon transport Xiang Chen, Weixuan Li, Adrian Diaz, Yang Li, and Youping Chen, Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611, USA David L. McDowell, Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA; School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA Address all correspondence to Xiang Chen at xiangchen@ufl.edu (Received 25 July 2017; accepted 10 October 2017)
Abstract This work presents the recent progress in the development of the concurrent atomistic-continuum (CAC) method for coarse-grained spaceand time-resolved atomistic simulations of phonon transport. Application examples, including heat pulses propagating across grain boundaries and phase interfaces, as well as the interactions between phonons and moving dislocations, are provided to demonstrate the capabilities of CAC. The simulation results provide visual evidence and reveal the underlying physics of a variety of phenomena, including phonon focusing, wave interference, dislocation drag, interfacial Kapitza resistance caused by quasi-ballistic phonon transport, etc. A new method to quantify fluxes in transient transport processes is also introduced.
Introduction Thermal transport has been studied for over 200 years. However, the strong interest in its micro/nanoscale details did not emerge until the late 1980s. The last decade has witnessed a remarkable focus on ever-decreasing scales, with modeling and simulation playing a significant role. Unfortunately, due to the limited computational resources, it is still challenging to move up from the atomic and nanoscale to model phonon interactions with mesoscale defect structures in lattices. It remains an inherently multiscale computational challenge.[1] After decades of development, there are several computational tools for phonon transport that have provided the community with very useful insight. As one of the pioneering methods in simulating phonon transport, the Boltzmann transport equation (BTE), with the help of recently developed efficient Monte Carlo algorithms, has been extended for the study of mesoscale material systems.[2,3] In BTE, the defects are not resolved in realistic simulation domains, but are considered indirectly through the extrinsic relaxation time of phonons. The relaxation time, together with other information regarding phonons, then needs to be obtained from either phenomenologic models or other methods at lower length scale such as the first-principles approach based on the density functional theory (DFT), the molecular dynamics (MD) simulation, or the atomistic Green’s function (AGF) method. However, these methods currently cannot realistically represent irregular defect structures that extend to the mesoscale, e.g., incoherent grain boundaries (GBs), multiple defects, moving dislocations,
etc. Simulating phonon interf
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