High P-T transformations of nitrogen to 170GPa

Abstract

X-ray diffraction and optical spectroscopy techniques are used to characterize stable and metastable transformations of nitrogen compressed up to 170 GPa and heated above 2500 K . X-ray diffraction data show that ϵ - N 2 undergoes two successive structural changes to complex molecular phases ζ at 62 GPa and a newly discovered κ at 110 GPa . The latter becomes an amorphous narrow gap semiconductor on further compression and if subjected to very high temperatures ( ∼ 2000 K ) crystallizes to the crystalline cubic-gauche-N structure ( cg - N ) above 150 GPa . The diffraction data show that the transition to cg - N is accompanied by 15% volume reduction.