Pressure-induced phase transition in hydrogen-bonded supramolecular adduct formed by cyanuric acid and melamine.
Single-crystal samples of the 1:1 adduct between cyanuric acid and melamine (CA.M), an outstanding case of noncovalent synthesis, have been studied by Raman spectroscopy and synchrotron X-ray diffraction in a diamond anvil cell up to pressures of 15 GPa. The abrupt changes in Raman spectra around 4.4 GPa have provided convincing evidence for pressure-induced structural phase transition. This phase transition was confirmed by angle dispersive X-ray diffraction (ADXRD) experiments to be a space group change from C2/m to its subgroup P2(1)/m. On release of pressure, the observed transition was irreversible, and the new high-pressure phase was fully preserved at ambient conditions. We propose that this phase transition was due to supramolecular rearrangements brought about by changes in the hydrogen bonding networks.
Wang
Kai
K
State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, PR China.
Duan
Defang
D
Wang
Run
R
Liu
Dan
D
Tang
Lingyun
L
Cui
Tian
T
Liu
Bingbing
B
Cui
Qiliang
Q
Liu
Jing
J
Zou
Bo
B
Zou
Guangtian
G