Calculations of the formation energy of vacancies in graphite crystals

Abstract

(1) An improved calculation is presented of the loss of π-electron resonance energy when a single carbon atom is ejected from an infinite graphite layer. This confirms a previous less reliable value 2.75β. (2) A careful discussion is provided of the possibility that, after the original carbon atom is ejected, its three neighbours change their electronic structure from trigonal sp 2 π hybridization to something closer to a divalent s 2 p 2 condition. Ignorance of the numerical values of certain quantities prevents a final decision; but on balance it appears a little unlikely that this occurs. (3) It is shown that when two single vacancies in the same plane unite to form a divacancy, there is an amount of energy released, which probably lies in the range 4–6 eV. In the course of these calculations it is shown that the loss of π-electron energy when 1, 2 or 4 carbon atoms are removed from a layer is 2.75 ± 0.01 β, 4.52 ± 0.01 β and 8.65 ± 0.04 β respectively.