Thermal conductivity of one-, two- and three-dimensional carbon

TL;DR

This study investigates the thermal conductivity of various carbon structures, revealing schwarzites have significantly lower thermal conductivity than nanotubes and graphene, due to reduced phonon transport properties, with implications for thermoelectric applications.

Contribution

It provides the first detailed comparison of thermal conductivity across 1D, 2D, and 3D carbon allotropes, highlighting schwarzites' potential for thermoelectric devices.

Findings

Schwarzites have thermal conductivity two orders of magnitude lower than nanotubes and graphene.

Phonon group velocities and mean free paths are significantly smaller in schwarzites.

Schwarzites' properties suggest potential for high-efficiency all-carbon thermoelectric technology.

Abstract

Carbon atoms can form structures in one, two, and three dimensions due to its unique chemical versatility. In terms of thermal conductivity, carbon polymorphs cover a wide range from very low values with amorphous carbon to very high values with diamond, carbon nanotubes and graphene. Schwarzites are a class of three-dimensional fully covalent sp$^2$-bonded carbon polymorphs, with the same local chemical environment as graphene and carbon nanotubes, but negative Gaussian curvature. We calculate the thermal conductivity of a (10,0) carbon nanotube, graphene, and two schwarzites with different curvature, by molecular dynamics simulations based on the Tersoff empirical potential. We find that schwarzites present a thermal conductivity two orders of magnitude smaller than nanotubes and graphene. The reason for such large difference is explained by anharmonic lattice dynamics calculations, which show that phonon group velocities and mean free paths are much smaller in schwarzites than in nanotubes and graphene. Their reduced thermal conductivity, in addition to tunable electronic properties, indicate that schwarzites could pave the way towards all-carbon thermoelectric technology with high conversion efficiency.