Formation of Hexagonal Diamond by Room Temperature Compression of Graphite

Abstract

In situ X-ray observation under high pressure was carried out to investigate the phase transformation in graphite induced by room temperature compression. Several diffraction peaks of the high pressure phase were clearly observed and could be indexed as a hexagonal diamond structure. The diffraction profiles from two different directions support the orientation relationship of the martensitic transformation from graphite to hexagonal diamond previously proposed. This hexagonal diamond has a large bulk modulus comparable to the cubic diamond.