Effects and correction of angular momentum non-conservation in RNEMD for calculating thermal conductivity
HA Yang and BY Cao, COMPUTATIONAL MATERIALS SCIENCE, 183, 109753 (2020).
The effects of angular momentum non-conservation in reverse non- equilibrium molecular dynamics (RNEMD) for thermal conductivity calculation are investigated. The velocity swapping operation in RNEMD results in an abnormal angular momentum flux when the center-of-mass velocity of heat source is considerable. The angular momentum is found to motivate a nonphysical wave motion at high heat flux, which was regarded as a novel heat conduction mechanism in earlier researches. This additional heat transport channel may lead to a non-physical increase in the computed thermal conductivity. Therefore, we propose an improved RNEMD, in which the hottest/coldest atoms are selected in center-of-mass frames. The results show that the improved RNEMD can greatly reduce the nonphysical correlation at any heat flux, eliminate the wave motion mode, and give constant thermal conductivity. Our research reveals a nonphysical effect from angular momentum non- conservation in RNEMD, and provides an improved RNEMD for heat transport in solid materials.
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