▎ 摘　　要

Geometric and electronic structures of a two-dimensional covalent network, consisting of [5.5.5.5]-fenestratetraene and cyclooctatetraene frameworks, are studied, using density functional theory with the generalized gradient approximation. Because of these constituent units and their arrangement in a two-dimensional covalent network, this two-dimensional C allotrope has a metallic electronic structure with the Dirac nodal lines just below the Fermi level as in the case of other Spiro-graphene materials. This C sheet is thermally stable and has a relatively high total energy of approximately 600 meV/atom with respect to that of graphene, which is close to other spiro-graphene materials, owing to its rippled covalent networks of sp(2) and sp(3) C atoms.