PhD Laurent Massi

"Studies of defects in brown and hydrogen-rich diamonds"

Laurent Massi, 15 September, 2006.

This study concerns the origin of brown coloration and identification of H-related centres in natural diamonds. There are four main causes for brown colour; the most frequent is plastic deformation, which is associated with “amber centres” defects. These defects, present in type I diamonds, are correlated with the brown colour intensity. The most common, AC1, is exclusively present in the graining and may be a defective A Étude de défauts dans les diamants bruns Laurent Massi - 2 372 006 : Etudes des défauts dans les diamants bruns et les diamants riches en hydrogène. aggregate. Others causes of brown colour are, in order of decreasing frequency: the presence of H-related centres, the “brown Ib” category (whose colour is possibly related to a distribution of defects) and lastly, probably indirectly, the presence of CO2. In the second section we analyze various H-rich diamonds and classified them by colour (essentially brown, yellow, green, grey and black) and by infrared active H-related systems. A scarce system, the “H-complex”, is found in so called “ABC” diamonds. Chameleon diamonds, which come from a part cuboid growth and are hydrogen containing, are thermo- and photochromic. We propose as a model for the X-chrome centre, a nitrogen - hydrogen complex. Lastly, we show that new H-related centres are localised in the cuboid sectors of inhomogeneous diamonds. We summarize all new infrared absorptions, and indicate potential correlations.

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