Density-functional study of nonmolecular phases of nitrogen: Metastable phase at low pressure

In first-principles variable-cell-shape molecular dynamics simulations and structural optimizations of nitrogen at pressures of 0--500 GPa, the phase with lowest enthalpy at high pressures, BP, was found to transform at low pressures into a new, metastable, metallic phase with a chainlike structure. The latter may possibly be related to a metastable nonmolecular phase that was recently observed experimentally at low temperatures and pressures.