Optimizing the thermoelectric performance of graphyne nanotube via applying radial strain

Abstract

Graphyne nanotubes (GNTs) are a new kind of one-dimensional carbon nanomaterials containing both sp and sp2 hybridization states. In this paper, taking gamma-GNTs as an example, we investigate the effect of radial strain on the thermoelectric conversion efficiency by means of nonequilibrium Green's function method as implemented in the density functional based tight-binding framework. The results reveal that the thermoelectric figure of merit could be obviously improved by applying appropriate radial strain. Such enhancement mainly originates from the reserved pristine electronic transport properties and significant suppressed phononic thermal conductance. However, as radial strain increases further, such enhanced thermoelectric performance will be reduced rapidly, which is attributed to the serious electron scattering caused by the change of bonding configuration of GNTs. These phenomena are quite different from previous studies that axial strain has a weak influence on the thermoelectric performance of carbon nanotubes and graphene nanoribbons. The findings presented in this paper indicate that radial strain is a viable way to optimize the thermoelectric performance of GNTs and could provide helpful theoretical guideline for designing and fabricating GNT-based thermoelectrics.