Twinning of cubic diamond explains reported nanodiamond polymorphs

The unusual physical properties and formation conditions attributed to h-, i-, m- and n-nanodiamond polymorphs has resulted in their receiving much attention in the materials and planetary science literature. Their identification is based on diffraction features that are absent in ordinary cubic (c-...

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Bibliographic Details
Published in:Scientific reports 2015-12, Vol.5 (1), p.18381-18381, Article 18381
Main Authors: Németh, Péter, Garvie, Laurence A. J., Buseck, Peter R.
Format: Article
Language:English
Subjects:
639/301/357/537
704/445/849
Biocompatibility
Carbon
Chemical vapor deposition
Crystals
Diamonds
Diffraction
Humanities and Social Sciences
Investigations
Meteors & meteorites
multidisciplinary
Nanocrystals
Physical properties
Quantum dots
Science
Symmetry
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Summary:The unusual physical properties and formation conditions attributed to h-, i-, m- and n-nanodiamond polymorphs has resulted in their receiving much attention in the materials and planetary science literature. Their identification is based on diffraction features that are absent in ordinary cubic (c-) diamond (space group: Fd-3m). We show, using ultra-high-resolution transmission electron microscope (HRTEM) images of natural and synthetic nanodiamonds, that the diffraction features attributed to the reported polymorphs are consistent with c-diamond containing abundant defects. Combinations of {113} reflection and rotation twins produce HRTEM images and d-spacings that match those attributed to h-, i- and m-diamond. The diagnostic features of n-diamond in TEM images can arise from thickness effects of c-diamonds. Our data and interpretations strongly suggest that the reported nanodiamond polymorphs are in fact twinned c-diamond. We also report a new type of twin ( rotational), which can give rise to grains with dodecagonal symmetry. Our results show that twins are widespread in diamond nanocrystals. A high density of twins could strongly influence their applications.
ISSN:2045-2322
2045-2322
DOI:10.1038/srep18381