First-Principles Calculation of the Isotope Effect on Boron Nitride Nanotube Thermal Conductivity

Isotopic composition can dramatically affect thermal transport in nanoscale heat conduits such as nanotubes and nanowires. A 50% increase in thermal conductivity for isotopically pure boron ((11)B) nitride nanotubes was recently measured, but the reason for this enhancement remains unclear. To address this issue, we examine thermal transport through boron nitride nanotubes using an atomistic Green's function transport formalism coupled with phonon properties calculated from density functional theory. We develop an independent scatterer model for (10)B defects to account for phonon isotope scattering found in natural boron nitride nanotubes. Phonon scattering from (10)B dramatically reduces phonon transport at higher frequencies and our model accounts for the experimentally observed enhancement in thermal conductivity.