Use of electrical conductivity experiments to study the phase diagram of carbon

Recent theoretical and experimental work on the properties of carbon at very high pressures indicates that the diamond phase may dominate the carbon phase diagram. The work of Yin and Cohen indicates that diamond may be the stable carbon phase to pressures as high as 20 Mbar. Recent work by Shaner, et al. is compatible with solid diamond on the Hugoniot at pressures up to 1.4 Mbar. Using previously developed techniques, we have carried out conductivity measurements on shock-compressed graphite to pressures in excess of 600 kbar and temperatures up to 5000/sup 0/K. No diamond - liquid transition was observed under the experimental conditions achieved