Three dimensional graphdiyne polymers with tunable band gaps.

Four three-dimensional graphdiyne polymers, namely Tri-C 18 , Hex-C 36 , Tri-C 54 , and Orth-C 72 , are predicted with first principles calculations. These carbon allotropes are constituted with interlinked sp 3 -hybridized carbon pillars and sp 2 -hybridized graphene-like nanoribbons. Graphdiyne polymers are energetically more stable than C 60 and graphdiyne, and show lower phase transition energy barriers from AA-graphdiyne than that of graphite–diamond transition. Except for the semimetallic Tri-C 18 , these polymers show narrow direct (or quasi-direct) band gap of 1.55–1.74 eV. The porous structure and the high in-plane Young’s modulus of graphdiyne sheet are inherited by these polymers. Meanwhile, a greatly enhanced Young’s modulus as high as ca . 1 TPa along the direction perpendicular to graphdiyne sheet and high hardness are developed in these systems. [ABSTRACT FROM AUTHOR]