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Title: Molecular simulations and lattice dynamics determination of Stillinger-Weber GaN thermal conductivity

The bulk thermal conductivity of Stillinger-Weber (SW) wurtzite GaN in the [0001] direction at a temperature of 300 K is calculated using equilibrium molecular dynamics (EMD), non-equilibrium MD (NEMD), and lattice dynamics (LD) methods. While the NEMD method predicts a thermal conductivity of 166 ± 11 W/m·K, both the EMD and LD methods predict thermal conductivities that are an order of magnitude greater. We attribute the discrepancy to significant contributions to thermal conductivity from long-mean free path phonons. We propose that the Grüneisen parameter for low-frequency phonons is a good predictor of the severity of the size effects in NEMD thermal conductivity prediction. For weakly anharmonic crystals characterized by small Grüneisen parameters, accurate determination of thermal conductivity by NEMD is computationally impractical. The simulation results also indicate the GaN SW potential, which was originally developed for studying the atomic-level structure of dislocations, is not suitable for prediction of its thermal conductivity.
Authors:
 [1] ; ;  [2] ;  [1] ;  [3]
  1. Rensselaer Nanotechnology Center, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)
  2. Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States)
  3. (United States)
Publication Date:
OSTI Identifier:
22492741
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 118; Journal Issue: 12; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ANHARMONIC CRYSTALS; DISLOCATIONS; EQUILIBRIUM; FORECASTING; GALLIUM NITRIDES; MEAN FREE PATH; MOLECULAR DYNAMICS METHOD; PHONONS; POTENTIALS; SIMULATION; THERMAL CONDUCTIVITY