Keywords: 
• 石墨炔 /
• 碳原子链 /
• sp/sp2杂化 /
• 第一性原理计算

Abstract: A new carbon allotrope—graphyne has attracted a lot of attention in the field of material sciences and condensedmatter physics due to its unique structure and excellent electronic,optical and mechanical properties.First-principles calculations based on the density functional theory (DFT) are performed to investigate the structures,energetic stabilities and electronic structures of γ-graphyne derivatives (γ-N).The studied γ-graphyne derivative consists of hexagon carbon rings connected by onedimensional carbon chains with various numbers of carbon atoms (N =1-6) on the chain.The calculation results show that the parity of number of carbon atoms on the carbon chains has a great influence on the structural configuration,the structural stability and the electronic property of the system.The γ-graphyne derivatives with odd-numbered carbon chains possess continuous C—C double bonds,energetically less stable than those with evennumbered carbon chains which have alternating single and triple C—C bonds.The electronic structure calculations indicate that γ-graphyne derivatives can be either metallic (when N is odd) or direct band gap semiconducting (when N is even).The existence of direct band gap can promote the efficient conversion of photoelectric energy,which indicates the advantage of γ-graphyne in the optoelectronic device.The band gaps of γ-2,4,6 are between 0.94 eV and 0.84 eV,the gap decreases with the number of triple C—C bonds increasing,and increases with the augment of length of carbon chains in γ-2,4,6.Our first-principles studies show that introducing carbon chains between the hexagon carbon rings of graphene gives us a method to switch between metallic and semiconducting electronic structures by tuning the number of carbon atoms on the chains and provides a theoretical basis for designing and preparing the tunable sop hybridized two-dimensional materials and nanoelectronic devices based on carbon atoms.