Structural transition in cold-compressed glassy carbon

Glassy carbon (GC) distinguishes itself from other carbon materials by its unique atomic structure and properties. Cold-compressed GC gives rise to new physical properties; however, the atomistic mechanism for the transitions remains elusive. In this study, by combining in situ high-pressure x-ray diffraction with first-principles calculations, we observe pressure-induced disappearance of the initial intermediate range order of GC, followed by formation of local tetrahedral structural domains and sp³ bonds. Correspondingly, the resistance of GC increases by four orders of magnitude during compression from ~20 to ~610.16em0exGPa. Both the structural and resistance transitions are partially reversible upon decompression, with noticeable hysteresis. Our results highlight the central role of layer distortions in inducing the sp²-to-sp³ bonding transition and provide the structural underpining for the various transitions observed in cold-compressed glassy carbon.