Affiliation:
1. School of Chemistry and Chemical Engineering Shandong University of Technology Zibo 255000 China
2. Analytical and Testing Center Shandong University of Technology Zibo 255000 China
3. School of Materials Science and Engineering Shandong University of Technology Zibo 255000 China
4. Department of Physics and Astronomy University of North Carolina at Chapel Hill Chapel Hill NC 27599‐3255 USA
Abstract
AbstractChanges in atomic bonding configuration in carbon from sp3 to sp2 are known to exist in certain structural defects in diamond, such as twin boundaries, grain boundaries, and dislocations, which have a significant impact on many properties of diamond. In this work, the atomic structure of fivefold twinning in detonation synthesized ultra‐dispersed diamonds is investigated using a combination of techniques, including spherical aberration‐corrected high‐resolution electron microscopy (HREM), HREM image simulations, and molecular mechanics (MM) calculations. The experimental HREM images reveal clearly that the fivefold twinning in diamond has two distinct structures. In addition to the concentric fivefold twins, where the core structure is the intersection of five {111} twinning boundaries, a new extended core structure with co‐hybridization of bonding is identified and analyzed in fivefold twinning. The atomic structure forming these fivefold twinning boundaries and their respective core structures is proposed to involve both the tetrahedral sp3 and planar graphitic sp2 bonding configurations, in which a co‐hybridized planar hexagon of carbon serves as a fundamental structural unit. The presence of this sp2‐bonded planar unit of hexagonal carbon rings in general grain boundaries is also discussed.
Subject
Biomaterials,Biotechnology,General Materials Science,General Chemistry