A defect molecule calculation for the vacancy in graphite

✍ Scribed by A.P.P. Nicholson; D.J. Bacon

• Publisher: Elsevier Science
• Year: 1975
• Tongue: English
• Weight: 916 KB
• Volume: 13
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/0008-6223(75)90028-7

✦ Synopsis

The defect-molecule calculations of Coulson et al. [2] of the electronic structure of a vacancy in graphite have been improved and extended to allow for symmetric relaxation. Various problems encountered previously[l, 21 have been shown to be due to the use of the Goeppert-Mayer and Sklar approximation. The rebonding forces on the nearest-neighbour atoms to the vacancy have been calculated, and a perfect-lattice model was used to describe lattice relaxation effects; the difficulties experienced in work on diamond and silicon[5,6] using an imperfect-lattice model were avoided. For the neutral vacancy, the stabilization energy, Ev, was found to be 1.44 eV, and the (symmetric) relaxation energy, E,, to be 3.32 eV. The neutral vacancy formation energy has been re-calculated, and using the above values for E, and E,, a value of 8.75 eV was obtained. This is somewhat higher than experimental estimates, but the difference may be explained by a high value for the formation entropy.