Hydrogen-bonding modification in biuret under pressure
Biuret (C2H5N3O2) has been studied to 30 GPa by Raman spectroscopy and 50 GPa by X-ray diffraction. Raman peaks exhibit shoulders and splitting that suggests that the molecules undergo reorientation in response to compression. These are observed in three pressure ranges: The first from 3-5 GPa, the second from 8-12 GPa, and finally from 16-20 GPa. The particular modes in the sample that are observed to change in the Raman are strongly linked to the molecular vibrations involving the N-H and the C?O bond, which are most strongly coupled to the hydrogenbonded lattice structure. The X-ray diffraction suggests that the crystal maintains a monoclinic structure to the highest pressures studied. Although there was a considerable degree of hysteresis observed in some X-ray runs, all the changes observed under pressure are reversible.
Journal of Physical Chemistry A
Borstad, G., & Ciezak-Jenkins, J. (2017). Hydrogen-bonding modification in biuret under pressure. Journal of Physical Chemistry A, 121 (4), 762-770. https://doi.org/10.1021/acs.jpca.6b09670