Thermoelectric Transport in Graphyne Nanotubes

The thermoelectric transport properties of graphyne nanotubes (GNTs) are investigated by using the nonequilibrium Green's function (NEGF) method, as implemented in the density functional based tight-binding (DFTB) framework. We find that both the band gap and thermoelectric figure of merit ZT show a damped oscillation with the tube diameter increased. Sign changes can be observed for the Seebeck coefficient, as the absolute value of the chemical potential increased, which is attributed to the minibands formation in the GNTs. In addition, the thermoelectric performance is reduced due to hydrogenation. Unexpectedly, the phonon thermal conductance of one of the hydrogenated GNTs is maintained, which is due to the counteraction of the surface roughness and the strain relaxation. Our investigations and findings are very important and of broad interest for expanding the graphyne community.