ABSTRACT
The phase behavior of carbon at high pressure and the search for carbon structures denser than diamond has been explored for decades showing large discrepancies, with many fundamental questions remaining unresolved. Here we show evidence of melting above the graphite-diamond-liquid (GDL) triple point (∼13 GPa, 4000 K) up to 50 GPa on samples recovered from single flash-heating events using spectroscopic and electron microscopic methods. The results show that for all pressures, diamond melts below the triple point temperature contradicting previous studies, most of which predict a positive slope of the melting curve.
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Acknowledgements
We thank C. Zhang for his help in the SEM operation and M. Somayazulu for his help with the Raman measurements, both at the Earth and Planets Laboratory, DC, USA. The authors gratefully acknowledge the scientific and technical assistance of the RMIT Microscopy & Microanalysis Facility, a linked laboratory of the Microscopy Australia.
Disclosure statement
No potential conflict of interest was reported by the author(s).