The reversible transition of graphite under high pressure: implications for the kinetic stability of lonsdaleite at intermediate temperature

摘要

Most of the basal planes in graphite are in the 2H sequence, which cannot be converted directly to either lonsdalrilc or diamond. The basal planes must be resequenced to 2H' or 3R before graphite can transform into lonsdulcite or diamond, respectively. At ambient temperature, the thermal energy is insufficient for this resequence. Without the resequencing of basal planes, graphite is compressed to form a structure with 1/7 of its bonds in sp3 form, and the remainder in distorted sp2it form. The sp3 bonds make the high-pressure phase optically transparent and electrically insulating. The dominant sp2jt bonds exhibit graphite-like Raman spectra. The majority distorted sp'it bonds destabilise the structure upon decompression. As a result, the minority sp3 bonds break, so the high-pressure phase reverts back to graphite at ambient pressure.