Unpaired π-spin density in defected graphite Original Research Article

Simple rules not requiring machine computation are enunciated to predict unpaired π-electron spins in graphitic structures, and these rules are illustrated in application to defected graphites with boundaries (i.e. with edges) or with local vacancy defects. The rules follow from a simple resonance-theoretic argument to give the number and general location of unpaired or nearly unpaired electrons. In addition a band-theoretic scenario for edge- or defect-localized unpaired electrons is outlined. Tight-binding molecular orbital theoretic computations are reported to compare against the resonance-theoretic predictions. The favorability of the comparisons tends to validate our easily applicable generalization of traditional resonance-theoretic organic chemical rationale, now in application to patterns of π electronic behavior for extended graphitic systems with defects.