New 2D nanosheets based on the octa-graphene

A class of 2D structures based on the architecture of the so called octa-graphene is proposed and theoretically investigated for the first time. The building blocks used to construct these structures are butadienes and linear carbon chains, with alternate single and triple bonds. The density functional theory (DFT) with periodic conditions is applied to study the electronic, structural, elastic and vibrational properties. These structures are stable and have interesting mechanical properties, as a large stiffness described by a 2D Young modulus varying within the range 116.00(N/m)≤Y2D≤308.36(N/m), values in the same order of magnitude of that found for graphene (Y2D∼340.0N/m). Another mechanical feature is the 2D Poisson ratio, found to be within the range 0.077≤ν2D≤0.628, a range of values impossible to cover with 3D materials. For their electronic structures, it was found that these materials are capable of going from metallic (C-based) to large band-gap semiconductors (BN-based) with indirect gap opening Eg∼5.49eV. The Raman spectrum for each one of these materials was calculated, revealing their vibration specific signatures that could be used to identify the existence of such materials in experimental studies. Another feature investigated was the interaction of the octagonal nanopores with Li atoms which could be useful for energy storage or gas separation membranes.