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High pressure Raman spectra of monoglycine nitrate single crystal
J O Carvalho1, G M Moura2, A O Dos Santos3
1Universidade Federal do Maranhão, CCSST, Imperatriz, MA 65900-000, Brazil; Instituto Federal do Tocantins, Araguaína, TO 77826-170, Brazil.
Summary
High pressure Raman spectroscopy reveals phase transitions in monoglycine nitrate crystals. These reversible transitions, likely due to hydrogen bond rearrangement, highlight the nitrate anion
Area of Science:
- Solid-state chemistry
- Materials science
- Spectroscopy
Background:
- Monoglycine nitrate (MGN) is a crystal with potential applications in nonlinear optics and materials science.
- Understanding its structural behavior under external stimuli like pressure is crucial for its technological utilization.
- Previous studies have explored its properties, but high-pressure phase transitions require further investigation.
Purpose of the Study:
- To investigate the high-pressure behavior of single-crystal monoglycine nitrate using Raman spectroscopy.
- To identify pressure-induced phase transitions and understand the underlying mechanisms.
- To determine the role of hydrogen bonding and nitrate anions in the crystal's stability.
Main Methods:
- Single-crystal Raman spectroscopy was employed to study monoglycine nitrate.
- Experiments were conducted under hydrostatic pressures up to 5.5 GPa.
- Analysis focused on changes in lattice modes and internal molecular vibrations.
Main Results:
- Two distinct pressure ranges (1.1-1.6 GPa and 4.0-4.6 GPa) exhibited significant changes in lattice modes.
- Discontinuities in the pressure dependence of lattice mode frequencies (dΩ/dP) were observed.
- Evidence suggests glycine molecule conformational changes and a phase transition involving lattice modes, with internal modes remaining unaffected, likely due to hydrogen bond rearrangements.
Conclusions:
- Monoglycine nitrate undergoes reversible pressure-induced phase transitions.
- These transitions are attributed to rearrangements in hydrogen bonding networks.
- Nitrate anions significantly contribute to the overall stability of the monoglycine nitrate crystal structure.
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