▎ 摘　　要

Using density functional theory, we study the energetics and electronic structures of graphene with monovacancies, surrounded by three pyridinic N atoms. Our calculations demonstrated that the detailed geometric structure and the formation energy of the defects do not depend on the mutual arrangement of the defects but on their density. The electronic structure is sensitive to the defect density and arrangement whether or not the pi network of C and N satisfies the Clar structure. A non-bonding pi state is induced at the Fermi level because of the sublattice imbalance of the pi network of C and N atoms.