Polymeric nitrogen: A review of experimental synthesis method, structure properties and lattice dynamic characterization from large scientific facilities and extreme spectroscopy perspectives

Pressure-Driven Energy Band Gap Narrowing of λ-N2

“…Studies have been focused on the molecular-to-polymeric transition in nitrogen due to its potential application as a high-energy-density material (HEDM). [17][18][19][20][21][22][23][24][25][26] Under high-pressure and high-temperature conditions (typically > 110 GPa, > 2000 K), the solid molecular nitrogen phase will dissociate, and the intermolecular triple bonds of N≡N will be ruptured, forming different single-bond polymeric phases such as cg-N, [18][19][20][21] LP-N, [22,23] PLP-N, [24] HLP-N, [23] and BP-N. [25,26] The polymeric-nitrogen synthetic pressure covers a wide regime, from 110 GPa to 244 GPa. [17] It is noted that the dense nitrogen is typi-cally optical opaque at so high pressures, which reflects the narrow energy band gap in the solid nitrogen.…”

“…[17][18][19][20][21][22][23][24][25][26] Under high-pressure and high-temperature conditions (typically > 110 GPa, > 2000 K), the solid molecular nitrogen phase will dissociate, and the intermolecular triple bonds of N≡N will be ruptured, forming different single-bond polymeric phases such as cg-N, [18][19][20][21] LP-N, [22,23] PLP-N, [24] HLP-N, [23] and BP-N. [25,26] The polymeric-nitrogen synthetic pressure covers a wide regime, from 110 GPa to 244 GPa. [17] It is noted that the dense nitrogen is typi-cally optical opaque at so high pressures, which reflects the narrow energy band gap in the solid nitrogen. This feature is suitable to be laser-heated by a near-infrared (∼ 1064 nm) ytterbium fiber laser (YFL) to overcome the energy barrier [17,21,24] from molecular to polymeric form.…”

“…[17] It is noted that the dense nitrogen is typi-cally optical opaque at so high pressures, which reflects the narrow energy band gap in the solid nitrogen. This feature is suitable to be laser-heated by a near-infrared (∼ 1064 nm) ytterbium fiber laser (YFL) to overcome the energy barrier [17,21,24] from molecular to polymeric form.…”