Ab Initio Calculations of New α-L_5-7a and β-L_5-7a Graphyne Polymorphic Varieties

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-L5-7a, β1-L5-7a, β2-L5-7a, β3-L5-7a and β4-L5-7a. The structure of layers γ1-L5-7a, γ2-L5-7a, and γ3-L5-7a is transformed into the structure of graphene layers by geometric optimization, and the graphyne layer γ4-L5-7a is transformed sp+sp2 layer L3-6-13. 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-L5-7a and β-L5-7a layers of graphyne is different from zero, so the new graphyne polymorphs should have metallic properties.