Electronic and structural properties of dense liquid and amorphous nitrogen

We present first-principles calculations of the structural and electronic properties of liquid nitrogen in the pressure-temperature range of 0--200 GPa and 2000--6000 K. Upon polymerization, the liquid becomes metallic, similar to what has been reported for the higher temperature atomic fluid. An explanation of the electronic properties of the transformed liquids and the differences with the electronic properties of insulating solid cubic-gauche nitrogen is given based on the structure and bonding character of these phases. The mechanism responsible for charge transport in polymeric nitrogen systems is examined in order to understand the semiconducting nature of low-temperature amorphous nitrogen.