Origins and Simulation of (002) Forbidden Reflections in Nanodiamonds: Implications for Sub-4 nm Nanodiamond Synthesis and Characterization

Abstract

So far, although the conception of the so-called “n-diamond” has been established for almost 30 years and widely cited as the critical evidence of Younger Dryas impact hypothesis, its crystallographic structure is still mysterious. Many speculations on the unexplained (002) forbidden reflections have been proposed. However, none of them has any convincible evidence or obeys the carbon orbital hybridization rules. According to the recent observation on sub-4 nm nanodiamond, we concluded that the “n-diamond” was not derived from the Fm3m crystallographic group. The unexplainable (002) forbidden reflection is caused by the spatial resolution limitation of HRTEM equipment and defocus on the target particles. According to the forbidden reflection rules, the defocus will lead to a topological obscure shadow in plane. Finally, experimental evidence of an individual sub-4 nm nanodiamond exhibits an observable transformation from cubic diamond to “n-diamond” with the appearance of (002) reflection, which proves our assumption. This work will contribute to the characterization technique for sub-4 nm nanodiamond synthesis.