Metallization and molecular dissociation of dense fluid nitrogen

TL;DR

This study investigates the high-pressure, high-temperature behavior of dense fluid nitrogen, revealing its transition from insulator to metal and providing insights into molecular dissociation and metallization processes.

Contribution

The paper experimentally establishes the conditions for metallization and fluid polymerization of nitrogen at extreme pressures and temperatures, advancing understanding of molecular dissociation under such conditions.

Findings

Metallization occurs above 125 GPa at 2500 K.

Transition from insulating to conducting fluid nitrogen observed.

Insights into molecular dissociation and metallization processes.

Abstract

Diatomic nitrogen is an archetypal molecular system known for its exceptional stability and complex behavior at high pressures and temperatures, including rich solid polymorphism, formation of energetic states, and an insulator-to-metal transformation coupled to a change in chemical bonding. However, the thermobaric conditions of the fluid molecular-polymer phase boundary and associated metallization have not been experimentally established. Here, by applying dynamic laser heating of compressed nitrogen and using fast optical spectroscopy to study electronic properties, we observe a transformation from insulating (molecular) to conducting dense fluid nitrogen at temperatures that decrease with pressure, and establish that metallization, and presumably fluid polymerization, occurs above 125 GPa at 2500 K. Our observations create a better understanding of the interplay between molecular dissociation, melting, and metallization revealing features that are common in simple molecular systems.