Papers by Keyword: Graphyne

Abstract: Calculations of the structural and energy parameters, band structure and density of electronic states of new structural varieties of graphyne have been performed by the density functional theory method. The initial structure of the nine polymorphs was theoretically constructed on the basis of the 5-7a graphene layer. As a result of the calculations, the structure of only five graphyne layers was found to be stable: α-L_5-7a, β1-L_5-7a, β2-L_5-7a, β3-L_5-7a and β4-L_5-7a. The structure of layers γ1-L_5-7a, γ2-L_5-7a, and γ3-L_5-7a is transformed into the structure of graphene layers by geometric optimization, and the graphyne layer γ4-L_5-7a is transformed sp+sp² layer L_3-6-13. The sublimation energy of the stable graphyne polymorphs varies from 6.66 to 6.78 eV/atom. The density of electronic states at the Fermi energy level for all α-L_5-7a and β-L_5-7a layers of graphyne is different from zero, so the new graphyne polymorphs should have metallic properties.

Abstract: Theoretical scheme is proposed for obtaining layered compounds consisting of carbon atoms in the sp-and sp²-hybridized states. This scheme is used to find the possibility of existing the seven basic structural modifications of graphyne: α-, β1-, β2-, β3-, γ1-, γ2-, and γ3-graphyne. The basic structural modifications of graphyne contain diatomic polyyne chains and consist only of carbon atoms in two different crystallographically equivalent states. Other nonbasic structural modifications of graphyne can be formed via the elongation of the carbyne chains and via the formation of graphyne layers with a mixed structure consisting of basic layer fragments. The geometrical optimization of the structure and the calculation of energy characteristics and electronic properties of graphyne layers were performed using ab initio calculations based on the density functional theory in the generalized gradient approximation. The energy of sublimation is found to be maximal for γ graphynes, which should be the most stable structural modifications of graphyne.

Abstract: Schemes of structural classification of carbon materials which are based on the types of chemical bonds formed in materials and the number of nearest neighbors with which each atom forms covalent bonds have been proposed. The classification schemes cannot only describe the known phases, but also are the methodological basis for the prediction of new phases and nanostructures. New phases can be obtained by linking, superpositioning or cutting of precursor structures.

Abstract: In this paper the mechanical properties of a series of hydrogen functionalized graphyne are investigated through acting tensile loads on the monolayer networks. Molecular dynamics simulations are performed to calculate the fracture strains and corresponding maximum forces for pristine graphyne along both armchair and zigzag directions. Furthermore, hydrogen functionalized graphynes with different functionalization sites are analyzed to investigate the effect of functionlization on the mechanical performance. Finally, Young's modulus of all the investigated architectures are computed. The obtained results show that monolayer graphyne is mechanically stable with high strength and stiffness, and the mechanical performance can be tuned through structure engineering and functionalization.