Recently, it was learned from Jilin University that the university, in collaboration with Sun Yat sen University, has formed a research team that has discovered a new pathway for the formation of hexagonal diamond from graphite through post graphite phase under high temperature and high pressure. High quality hexagonal diamond block materials have been artificially synthesized, with higher hardness than cubic diamond and good thermal stability. Hexagonal diamond, also known as "meteorite diamond", was first discovered in a meteorite crater in the United States and is theoretically predicted to be harder than cubic diamond. The formation conditions of hexagonal diamond are extremely strict, only in the nanometer size, and it coexists with meteorites. Therefore, there is still controversy over whether hexagonal diamond can be independent, and the artificial synthesis of pure phase hexagonal diamond is particularly challenging. Given the ultra-high pressure and high temperature conditions during the formation of hexagonal diamond, the research team designed a high-temperature and high-pressure experiment. Firstly, the structural changes of graphite under ultra-high pressure and high temperature of 50GPa were studied in situ using laser heated diamond anvil technology. It was found that graphite would form a high-pressure structure in the high-pressure range, and then hexagonal diamond was successfully obtained through local heating. The research team further combined large-scale molecular dynamics theory simulation to reveal the key role of graphite layer stacking configuration in the formation of hexagonal diamond structure, confirming a new path for graphite to form hexagonal diamond through post graphite phase. Under the conditions of 30GPa and 1400 ℃, the research team successfully prepared millimeter level highly oriented hexagonal diamond blocks, and found that their hardness was as high as 155 ± 9GPa, which was 40% higher than natural diamond. Under vacuum environment, their thermal stability could reach 1100 ℃, which was better than the 900 ℃ of nanodiamonds. This research not only provides strong evidence for the independent existence of hexagonal diamonds, but also provides an effective way to artificially synthesize pure phase hexagonal diamonds, adding new members with better performance to superhard materials and new carbon materials. It is also of great significance for a deeper understanding of the specific sources and major geological events of diamonds in meteorites. (New Society)