First-principle study of structure stability and electronic structures of graphyne derivatives

Abstract

A new carbon allotropegraphyne has attracted a lot of attention in the field of material sciences and condensed-matter 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 -graphyne derivatives ( -N). The studied -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 -graphyne derivatives with odd-numbered carbon chains possess continuous CC double bonds, energetically less stable than those with even-numbered carbon chains which have alternating single and triple CC bonds. The electronic structure calculations indicate that -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 -graphyne in the optoelectronic device. The band gaps of -2, 4, 6 are between 0.94 eV and 0.84 eV, the gap decreases with the number of triple CC bonds increasing, and increases with the augment of length of carbon chains in -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 s-p hybridized two-dimensional materials and nanoelectronic devices based on carbon atoms.