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Lookup NU author(s): Professor Patrick Briddon
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Models for radiation damage in graphite are reviewed and compared, leading to a re-examination of the contribution made by vacancies to annealing processes. A method based on density functional theory, using large supercells with orthorhombic and hexagonal symmetry, is employed to calculate the properties and behaviour of lattice vacancies and displacement defects. It is concluded that annihilation of intimate Frenkel defects marks the onset of recovery in electrical resistivity, which occurs when the temperature exceeds about 160 K. The migration of isolated monovacancies is estimated to have an activation energy of E-a approximate to 1.1 eV. Coalescence into divacancy defects occurs in several stages, with different barriers at each stage, depending on the path. The formation of pairs ultimately yields up to 8.9 eV energy, which is nearly 1.0 eV more than the formation energy for an isolated monovacancy. Processes resulting in vacancy coalescence and annihilation appear to be responsible for the main Wigner energy release peak in radiation-damaged graphite, occurring at about 475 K.
Author(s): Latham CD, Heggie MI, Alatalo M, Oberg S, Briddon PR
Publication type: Article
Publication status: Published
Journal: Journal of Physics: Condensed Matter
Print publication date: 07/03/2013
ISSN (print): 0953-8984
ISSN (electronic): 2160-6927
Publisher: Institute of Physics Publishing Ltd.
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