Synthesis and crystal structure of n-diamond

Allotropes of carbon based materials, such as graphite, fullerenes and nanotubes, and diamond are currently a focus of great interest. New diamond (n-diamond) has been proposed as a new carbon allotrope; its electron diffraction pattern matches that of cubic (Fd (3) over barm) diamond apart from some additional reflections that are forbidden for diamond, indexed as {200}, {222} and {420}. n-Diamond has been found experimentally for more than 10 years, yet its structure and stability are not unambiguously resolved, and some controversies still exist. A comprehensive review of recent developments in the experimental and theoretical knowledge of n-diamond is presented. Synthesis methods reported for n-diamond and transformation mechanisms from other carbon allotropes are discussed. The various crystal structure models proposed for n-diamond are summarised and critically assessed. The stability to aging and other properties of n-diamond are briefly considered. Finally, the potential for technological application of n-diamond as an electromagnetic absorber is discussed.