| Summary: | The energy states of π -electrons in a graphene nanoflake obtained from graphene, a well-known bipartite lattice or honeycomb lattice of carbon atoms, are studied using the tight-binding method. It is reported that the sublattice imbalance Δ N of the entire graphene nanoflake including vacancy clusters, which characterizes the electronic states, consists of those of the outer and inner edges. In nonzero-energy states, the electrons are evenly distributed between the sublattices A and B, regardless of the value of Δ N . In contrast, zero-energy states are ∣Δ N ∣-fold degenerate states where the electrons are unevenly distributed on either sublattice A or sublattice B. Occasionally, large or specific graphene nanoflakes have substantial zero-energy states, which are mixed states of the nonzero-energy states and zero-energy states.
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