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Lookup NU author(s): Dr Jon Goss,
Professor Patrick Briddon
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We examine the hydrogenated substitutional nitrogen pair defect, N-2-H, in diamond, with different charge states using density functional theory calculations. Neutral N-2-H is predicted to exhibit optical absorption in the 600 nm to near infrared range, hence contributing to colour. We suggest that it may be representative of a family of nitrogen-hydrogen complexes, which due to covalent nitrogen-hydrogen bonding could explain several observed absorptions. Changing the charge state leads to spontaneous geometric rearrangements, and we find the neutral charge state is thermodynamically metastable. The resultant negative-U behaviour suggests it is unstable as a donor. The structural changes with charge state may contribute to the thermochromic and photochromic behaviour of the so-called "chameleon" diamonds. (C) 2011 Elsevier B.V. All rights reserved.
Author(s): Goss JP, Ewels CP, Briddon PR, Fritsch E
Publication type: Article
Publication status: Published
Journal: Diamond and Related Materials
Print publication date: 14/05/2011
ISSN (print): 0925-9635
Publisher: Elsevier SA
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