Structure of the Diamond-lonsdaleite System
A High-Resolution Electron Microscopy (HREM) Study
Hexagonal diamond or lonsdaleite (2H) is a new form of carbon which was found in meteorites . For the first time it was obtained artificially  under conditions of static pressure exceeding 13 GPa and temperature greater than 1000 °C. Hexagonal diamond differs from the cubic one (3C) by the layers stacking. Crystal lattice of cubic diamond represent itself a sequence of atomic layers ABCABC..., whereas lonsdaleite lattice represents ABAB... stacking. Further, lonsdaleite was obtained mostly as a result of thermobaric treatment of carbon materials (for example, from graphite ). Britun V. et al. examined lonsdaleite obtained from graphite in high pressure chamber, and they have established that lonsdaleite is metastable martensite phase of carbon . In  authors have synthesized nanocrystalline cubic diamond powder from C60, which contained lonsdaleite layers. Also diamond particularly was transformed into lonsdaleite during the diamond powder annealing .
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This work was supported by the Ministry of Education and Science of Russian Federation within the framework of state contract N_o 12.527.12.5003.
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Dr Boris A Kulnitskiy (corresponding author via e-mail request)
Dr Igor A Perezhogin
Prof Dr Vladimir Blank
Technological Institute for Superhard and Novel Carbon Materials
Troitsk, Moscow, Russia