First-principles calculations of the single-bonded cubic phase of nitrogen

We performed the extensive first-principles simulations for understanding of the stability of complex structures of the nonmolecular nitrogen. We found that the single-bonded cubic phase of nitrogen, so-called cubic gauche structure (cg-N), is the most stable phase among these phases in high pressure, and predicted that a phase transition of cg-N from nonmetal to metal takes place at the pressure of $600\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. The bulk modulus, Young modulus, shear modulus, Poisson ratio, and band gap of cg-N were calculated that are quite well consistent with experimental data.