Structural and spectroscopic studies of nitrogen-carbon monoxide mixtures: Photochemical response and observation of a novel phase
Mixtures of nitrogen and carbon monoxide in two molar compositions (90-10 and 95-5 N2 - CO) have been studied with Raman spectroscopy, X-ray diffraction, and first-principles density functional theory. Near 16 GPa, there is a discontinuous change in the X-ray diffraction patterns indicating a transition to phase I, which is distinct from any known phase of nitrogen. With the help of theory, the X-ray diffraction pattern was indexed to a triclinic unit cell. The evolutionary crystal structure search also identified several metastable stoichiometries of C - O - N phases, which produce distinct signatures in the experimental Raman spectra, thus explaining anomalous Raman behavior. Decompression studies showed that phase I did not persist below the melt line of nitrogen and, as such, it can be concluded that all observations are reversible.
Journal of Chemical Physics
Ciezak-Jenkins, J., Steele, B., Borstad, G., & Oleynik, I. (2017). Structural and spectroscopic studies of nitrogen-carbon monoxide mixtures: Photochemical response and observation of a novel phase. Journal of Chemical Physics, 146 (18) https://doi.org/10.1063/1.4983040