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Raman spectra of ammonia borane: low frequency lattice modes
C Ziparo1, D Colognesi, A Giannasi
1Consiglio Nazionale delle Ricerche - Istituto dei Sistemi Complessi, via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy.
The Journal of Physical Chemistry. A
|July 17, 2012
Summary
Raman spectroscopy reveals ammonia borane
Area of Science:
- Solid-state chemistry
- Materials science
- Spectroscopy
Background:
- Ammonia borane is a hydrogen-rich material with potential applications in hydrogen storage.
- Understanding its phase transitions is crucial for material characterization and application.
- Low-temperature studies provide insights into fundamental material properties.
Purpose of the Study:
- To investigate the Raman spectrum of ammonia borane at low temperatures.
- To analyze the orthorhombic-to-tetragonal phase transition using Raman spectroscopy.
- To elucidate the changes in lattice modes and molecular behavior during the phase transition.
Main Methods:
- Raman spectroscopy measurements at 15 K and across the 225 K phase transition.
- Low-frequency lattice mode analysis.
- Density functional theory (DFT) calculations for mode assignment.
Main Results:
- Comprehensive Raman spectra of ammonia borane were obtained at 15 K.
- Spectroscopic data across the phase transition indicated increasing orientational disorder.
- The results are consistent with the lattice constants equalization observed in the tetragonal phase.
Conclusions:
- Raman spectroscopy effectively probes the phase transition in ammonia borane.
- The transition involves significant changes in molecular orientational disorder.
- DFT calculations aid in the detailed assignment of Raman active modes.
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