Molecular dynamics simulation of thermal transport properties for boron nitride nanotubes

The Boltzmann-Peierls phonon transport equation (BTE) and non-equilibrium molecular dynamics simulation (NEMD) are used to investigate the thermal transport properties of boron nitride nanotubes (BNNTs). First, the thermal-mechanical coupling is explored using NEMD. Then, by combining BTE and NEMD, the influence of temperature and length is investigated. Quantum correction is used to extend the range over which NEMD can be used. The results demonstrate that under low-strain conditions, the thermal conductivity decreases with increasing tensile or compressive strain. Then the phonon density of state (PDOS) is used to analyze the trends in thermal transport properties theoretically; it is found that the variations in thermal transport properties under tension are caused by changes in the phonon modes, and that under compression changes are induced by the flection of the BNNT structure. The BNNT thermal conductivity increases linearly with increasing temperature because of the quantum effect at low temperatures, and it decreases significantly as the temperature reaches a certain value. When the BNNT length is less than 120 nm, the BNNT's ballistic characteristics weaken with increasing length, but it also performs ballistic characteristic mainly, and thermal conductivity (κ) and length (L) obey the relationship κ ∞ L ^α.