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Updated: Mar 6, 2026

High Pressure Single Crystal Diffraction at PX^2
Published on: January 16, 2017
Bulk hexagonal diamond
Shoulong Lai1, Xigui Yang2, Jiuyang Shi3
1Henan Key Laboratory of Diamond Materials and Devices, Key Laboratory of Integrated Circuit, Ministry of Education, School of Physics, Zhengzhou University, Zhengzhou, China.
Abstract:
Known as the 'ultimate semiconductor', cubic diamond (CD) has gained substantial interest both scientifically and industrially. Its polymorph, hexagonal diamond (HD), is even more intriguing because of its fascinating properties associated with the meteorite impacts1-8. As no solid experimental evidence has been provided to prove its existence, the physical properties of HD remain largely unexplored. Here we report the synthesis of millimetre-sized, phase-pure HD from highly oriented pyrolytic graphite (HOPG) compressed along the c-axis at elevated temperatures. Combining advanced structural characterizations and theoretical simulations, we confirm the identity of HD and clarify the transformation pathway from graphite. Bulk HD exhibits a slightly higher hardness than CD and high thermal stability. These findings resolve the long-standing controversy on the existence of HD as a discrete carbon phase and provide new insight into the graphite-to-diamond phase transition, paving the way for future research and practical use of HD in advanced technological applications.
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