Heat conduction of single-walled carbon nanotube isotope-superlattice structures: A molecular dynamics study

TL;DR

This study uses molecular dynamics simulations to explore how superlattice structures in single-walled carbon nanotubes affect heat conduction, revealing a critical period where thermal transport mechanisms shift.

Contribution

It introduces a detailed analysis of the crossover from zone-folding effects to boundary resistance in SWNT superlattices, highlighting the dependence on phonon mean free paths.

Findings

Identified a critical superlattice period with minimum thermal conductivity.

Demonstrated the dominant physics switch from zone-folding to boundary resistance.

Showed superlattice structures outperform alloy structures in reducing thermal conductivity.

Abstract

Heat conduction of single-walled carbon nanotubes (SWNTs) isotope-superlattice is investigated by means of classical molecular dynamics simulations. Superlattice structures were formed by alternately connecting SWNTs with different masses. On varying the superlattice period, the critical value with minimum effective thermal conductivity was identified, where dominant physics switches from zone-folding effect to thermal boundary resistance of lattice interface. The crossover mechanism is explained with the energy density spectra where zone-folding effects can be clearly observed. The results suggest that the critical superlattice period thickness depends on the mean free path distribution of diffusive-ballistic phonons. The reduction of the thermal conductivity with superlattice structures beats that of the one-dimensional alloy structure, though the minimum thermal conductivity is still slightly higher than the value obtained by two-dimensional random mixing of isotopes.