supercell of the big number of unit cells, periodically extended with images of the original vacancy. Spin orientations in each supercell become the same, yielding seemingly a ferromagnetic signature of total magnetization even in the absence of a spin-spin interactions. Nevertheless, we believe that a magnetic ordering in a system should be achieved by exchange interactions between the magnetic moments. A numeric computation reveals that a vacancy in graphene [@psn08; @pgsp06; @ubgg10] introduces a semi-localized $\pi$-midgap state with Coulomb-like $\sim 1/r$ decay potential. The single-atom defects create in the graphene a quasi-localized state at the Fermi level [@rgs00; @mf89; @rmg05; @pgsp06]. The graphene structure can be viewed as two interpenetrating hexagonal sublattices of carbon atoms labeled as $A$ and $B$ ones, forming a bipartite lattice. A defect introduced into the $A$ sublattice results in a quasi-localized state due to the $p_z$ orbitals of carbon atoms in the $B$ sublattice and vice versa. A short-range repulsive Hubbard interactions between vacancies at higher concentrations and with half-filled band may result in a ground state with total spin $S=|N_A-N_B|/2$ according to Lieb’s theorem [@lieb89], where $N_A$ and $N_B$ are the number of vacancies in $A$ and $B$ sublattices, correspondingly, of a bipartite lattice. 