A C20-based 3D carbon allotrope with high thermal conductivity

Abstract

Stimulated by the high thermal conductivity of diamond together with the light mass and rich resources of carbon, a great deal of effort has been devoted to the study of the thermal conductivity of carbon-based materials. In this work, we systematically study the thermal transport properties of a three dimensional (3D) C₂₀ fullerene-assembled carbon allotrope, HSP3-C₃₄, in which all carbon atoms are in sp³ hybridization. The stability of HSP3-C₃₄ is confirmed and its thermal conductivity is obtained by using first principles calculations combined with solving the linearized phonon Boltzmann transport equation. At room temperature, the thermal conductivity of HSP3-C₃₄ is 731 W m⁻¹ K⁻¹, which is larger than those of many 3D carbon allotropes, such as BCO-C₁₆ (452 W m⁻¹ K⁻¹), 3D graphene (150 W m⁻¹ K⁻¹) and T-carbon (33 W m⁻¹ K⁻¹). A detailed analysis of its phonons reveals that three acoustic branches are the main heat carriers at room temperature, and the optical branches gradually become important with increasing temperature. A further study on the harmonic and anharmonic properties of HSP3-C₃₄ uncovers that the main reasons for the high thermal conductivity are the weak anharmonicity and large group velocity resulting from the strong sp³ bonding. This study provides new insights on searching for carbon allotropes with high thermal conductivity.