A new C20-based 3D carbon allotrope with high thermal conductivity
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 thermal conductivity of carbon-based materials. In this work, we propose a new three dimensional (3D) C20 fullerenes 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 up to 731 W/mK, which is larger than that of many 3D carbon allotropes, such as BCO-C16 (452 W/mK), 3D graphene (150 W/mK) and T-carbon (33 W/mK). A detailed analysis of its phonons reveals that three acoustic branches are main heat carriers at room temperature, and the optical branches gradually become important with increasing temperature. A further study on 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 the design of new carbon allotropes with high thermal conductivity.