a tendency of clustering of vacancies into big holes, instead of homogeneous distribution of isolated vacancies over the system in the irradiation process. It is worthy to note that total energy calculations have been done in Ref. \[\] for nanoholes of various sizes, containing up to 60 vacancies, in a big supercell with 288 carbon atoms in graphene by applying ab-initio DFT method. Although the number of possible holes for a given number vacancies $N$ increases sharply with $N$, it is hard task to calculate all possible cluster structures with higher N. Nevertheless, the results of Ref. \[\] yield extremely useful information on stability and magnetism of holes with a great number of vacancies.

Such kind of “[*segregation*]{}” seems to be a result of two-dimensional character of the graphene sheet where an off-diagonal long range order (ODLRO) is absent. The crystalline structure of the graphene is controlled by power-like order. Correlations of the vacancies seem to be managed also with power-like order, which compete with correlations between the carbon atoms in the structure. In order to understand the vacancy hole formation and healing mechanism in a graphene layer, a phenomenological kinetic model is employed by us for a migration of 