We propose an optimized scheme to determine the smearing parameter in the Gaussian function that is used to replace the Dirac δ function in the first Brillouin zone sampling. The broadening width is derived by analyz...We propose an optimized scheme to determine the smearing parameter in the Gaussian function that is used to replace the Dirac δ function in the first Brillouin zone sampling. The broadening width is derived by analyzing the difference of the results from the phase-space method and Gaussian broadening method. As a demonstration, using the present approach,we investigate the phonon transport in a typical layered material, graphite. Our scheme is benchmarked by comparing with other zone sampling methods. Both the three-phonon phonon scattering rates and thermal conductivity are consistent with the prediction from the widely used tetrahedron method and adaptive broadening method. The computational efficiency of our scheme is more than one order of magnitude higher than the two other methods. Furthermore, the effect of fourphonon scattering in phonon transport in graphite is also investigated. It is found that four-phonon scattering reduces the through-plane thermal conductivity by 10%. Our methods could be a reference for the prediction of thermal conductivity of anisotropic material in the future.展开更多
The knowledge of interfacial thermal conductance(ITC)is key to understand thermal transport in nanostructures.The non-equilibrium molecular dynamics(NEMD)simulation is a useful tool to calculate the ITC.In this study,...The knowledge of interfacial thermal conductance(ITC)is key to understand thermal transport in nanostructures.The non-equilibrium molecular dynamics(NEMD)simulation is a useful tool to calculate the ITC.In this study,we investigate the impact of thermostat on the prediction of the ITC.The Langevin thermostat is found to result in larger ITC than the Nose-Hoover thermostat.In addition,the results from NEMD simulations with the Nose-Hoover thermostat exhibit strong size effect of thermal reservoirs.Detailed spectral heat flux decomposition and modal temperature calculation reveal that the acoustic phonons in hot and cold thermal reservoirs are of smaller temperature difference than optical phonons when using the Nose-Hoover thermostat,while phonons in the Langevin thermostat are of identical temperatures.Such a nonequilibrium state of phonons in the case of the Nose-Hoover thermostat reduces the heat flux of low-to-middle-frequency phonons.We also discuss how enlarging the reservoirs or adding an epitaxial rough wall to the reservoirs affects the predicted ITC,and find that these attempts could help to thermalize the phonons,but still underestimate the heat flux from low-frequency phonons.展开更多
基金support from the National Natural Science Foundation of China (Grant No. 51706134)。
文摘We propose an optimized scheme to determine the smearing parameter in the Gaussian function that is used to replace the Dirac δ function in the first Brillouin zone sampling. The broadening width is derived by analyzing the difference of the results from the phase-space method and Gaussian broadening method. As a demonstration, using the present approach,we investigate the phonon transport in a typical layered material, graphite. Our scheme is benchmarked by comparing with other zone sampling methods. Both the three-phonon phonon scattering rates and thermal conductivity are consistent with the prediction from the widely used tetrahedron method and adaptive broadening method. The computational efficiency of our scheme is more than one order of magnitude higher than the two other methods. Furthermore, the effect of fourphonon scattering in phonon transport in graphite is also investigated. It is found that four-phonon scattering reduces the through-plane thermal conductivity by 10%. Our methods could be a reference for the prediction of thermal conductivity of anisotropic material in the future.
基金the support from the National Natural Science Foundation of China(Grant No.51706134)supported by the Center for High Performance Computing at Shanghai Jiao Tong University。
文摘The knowledge of interfacial thermal conductance(ITC)is key to understand thermal transport in nanostructures.The non-equilibrium molecular dynamics(NEMD)simulation is a useful tool to calculate the ITC.In this study,we investigate the impact of thermostat on the prediction of the ITC.The Langevin thermostat is found to result in larger ITC than the Nose-Hoover thermostat.In addition,the results from NEMD simulations with the Nose-Hoover thermostat exhibit strong size effect of thermal reservoirs.Detailed spectral heat flux decomposition and modal temperature calculation reveal that the acoustic phonons in hot and cold thermal reservoirs are of smaller temperature difference than optical phonons when using the Nose-Hoover thermostat,while phonons in the Langevin thermostat are of identical temperatures.Such a nonequilibrium state of phonons in the case of the Nose-Hoover thermostat reduces the heat flux of low-to-middle-frequency phonons.We also discuss how enlarging the reservoirs or adding an epitaxial rough wall to the reservoirs affects the predicted ITC,and find that these attempts could help to thermalize the phonons,but still underestimate the heat flux from low-frequency phonons.
