The contribution made by lattice vacancies to the Wigner effect in radiation-damaged graphite
2013 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 25, no 13, 135403Article in journal (Refereed) Published
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 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. Migration of isolated monovacancies is estimated to have an activation energy Ea ≈ 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.
Place, publisher, year, edition, pages
2013. Vol. 25, no 13, 135403
Research subject Scientific Computing
IdentifiersURN: urn:nbn:se:ltu:diva-16152DOI: 10.1088/0953-8984/25/13/135403Local ID: fbf0395a-7baf-49ee-8919-2ec96908a566OAI: oai:DiVA.org:ltu-16152DiVA: diva2:989128
Validerad; 2013; Bibliografisk uppgift: Article no 135403; 20130305 (latham)2016-09-292016-09-29Bibliographically approved