Twinning of cubic diamond explains reported nanodiamond polymorphs
Description
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 <011> 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 (<121> 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.
Date Created
The date the item was original created (prior to any relationship with the ASU Digital Repositories.)
2015-12-16
Agent
- Author (aut): Nemeth, Peter
- Author (aut): Garvie, Laurence
- Author (aut): Buseck, Peter
- Contributor (ctb): College of Liberal Arts and Sciences
- Contributor (ctb): School of Earth and Space Exploration
- Contributor (ctb): Center for Meteorite Studies