title: Hydrogen-Bonding Modification in Biuret Under Pressure.
abstract: 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 hydrogen-bonded 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.
authors.affiliation: RDRL-WML-B, U.S. Army Research Laboratory , Aberdeen Proving Ground, Maryland 21005, United States.
authors.forename: Gustav M
authors.identifier: http://orcid.org/0000-0002-3087-6260
authors.initials: GM
authors.lastname: Borstad
authors.affiliation: RDRL-WML-B, U.S. Army Research Laboratory , Aberdeen Proving Ground, Maryland 21005, United States.
authors.forename: Jennifer A
authors.identifier: http://orcid.org/0000-0002-7866-3539
authors.initials: JA
authors.lastname: Ciezak-Jenkins