High-Pressure Photoinduced Synthesis of Polynitrogen in δ and ϵ Nitrogen Crystals Substitutionally Doped with CO

Abstract

A polynitrogen material was obtained by high pressure laser irradiation of nitrogen crystals containing 5% and 10% of CO molecules as substitutional impurities. The instability of CO under pressure generates poly-CO aggregates which, once irradiated with the 514.5 nm laser line, quantitatively react with the neighboring N2 molecules. DFT calculations and ab initio molecular dynamics simulations provided insight on the reaction mechanism and on the reaction products. The obtained extended material was characterized by FTIR and Raman spectroscopy, and the spectra were interpreted according to the comparison with C–N extended systems and computational data. Besides amorphous a-C:N-like domains, single bonded nitrogen clusters with C═O terminations are likely present. The extended material does not decompose on releasing pressure and can be quenched down to 1–2 GPa across the melting of N2. A sudden decomposition under high power irradiation of the product prepared by a crystal containing 10% of CO molecules ...