Novel carbon allotropes in all-sp 2 bonding networks: self-assembling design and first-principles calculations.

Compared with traditional structure prediction methods, the purposeful bottom-up approach is better able to obtain structures with specified performance. In this study, we established two novel carbon phases in purely sp-bonded networks, termed H6-carbon and H6-carbon, using a self-assembling approach. These carbyne-connected carbon allotropes had helix chains joined by cumulative double-bond chains. We certified the new carbon allotropes to be dynamically and mechanically stable. Both of these carbon allotropes exhibited excellent mechanical properties, and they had metallic and superconductive characteristics featuring superconducting transition temperatures of 10 K (H6-carbon) and 7.4 K (H6-carbon), respectively. These results provide an important strategy for the design of novel carbon allotropes with specified properties.