Polymerization, shock cooling, and the high-pressure phase diagram of nitrogen

The trajectory of states passed through by the nitrogen Hugoniot has been followed from the normal molecular liquid up to the dense plasma state near 10(6) GPa. A phase diagram is proposed that is very similar to one reported for phosphorous. The nitrogen phase diagram connects the recently observed molecular to cg-N polymer phase transition in the solid at 110 GPa, to a liquid-polymer phase line obtained from of shock cooling measurements. At much higher pressures, calculations of the Hugoniot predict that ionization of the tightly bound inner L and K electron shells lead to compression maxima of approximately 5-6 fold near 1000 GPa (T similar to 3.5 10(5) K) and 40 000 GPa (T similar to 2.3 10(6) K), respectively.