Raman spectroscopy of melamine at high pressures up to 60 GPa

Abstract

In this work, the Raman scattering of melamine was studied under high pressure up to 60 GPa. The behavior of the most intensive peaks of the Raman spectrum of melamine, 677 cm⁻¹ and 985 cm⁻¹ modes, and their line widths do not show any phase transition or indication of formation of sp ³ bonds. Comparing the behavior of the line width of the Raman peaks of graphite under pressure and that of melamine leads us to conclude that the s-triasine (C–N) ring is more rigid than the C–C graphite ring. High pressure results with melamine suggest that the direct phase transition g-C₃N₄ to dense C₃N₄ phase should occur above 60 GPa.

Keywords:

• Raman scattering
• C₃N₄
• graphite
• high pressure

Acknowledgements

This work was supported by U.S. Department of Energy Grant No. DE-FG02-07ER46408. We thank Dr Tkachev for helping us load the DAC with Ne at the GSECARS. The use of the GSECARS facility is supported by the National Science Foundation-Earth Sciences (EAR-0622171) and Department of Energy-Geosciences (DE-FG02-94ER14466). The use of the APS was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.