Pressure-induced phase transitions in L-leucine crystal
Article first published online: 15 AUG 2008
Copyright © 2008 John Wiley & Sons, Ltd.
Journal of Raman Spectroscopy
Volume 40, Issue 1, pages 46–51, January 2009
How to Cite
Façanha Filho, P. F., Freire, P. T. C., Melo, F. E. A., Lemos, V., Mendes Filho, J., Pizani, P. S. and Rossatto, D. Z. (2009), Pressure-induced phase transitions in L-leucine crystal. J. Raman Spectrosc., 40: 46–51. doi: 10.1002/jrs.2071
- Issue published online: 7 JAN 2009
- Article first published online: 15 AUG 2008
- Manuscript Accepted: 13 MAY 2008
- Manuscript Received: 28 MAR 2008
- Brazilian agencies
- amino acid;
- hydrogen bond;
- high pressure
Raman spectra of a crystal of L-leucine, an essential amino acid, were obtained for pressures between 0 and 6 GPa. The results show anomalies at three pressure values, one between 0 and 0.46 GPa, another between 0.8 and 1.46 GPa, and a third at P ∼ 3.6 GPa. The first two anomalies are characterized by the disappearance of lattice modes (which can indicate occurrence of phase transitions), the appearance of several internal modes, or the splitting of modes of high wavenumbers. The changes of internal modes are related to CH and CH3 unit motions as well as hydrogen bonds, as can be inferred from the behavior of bands associated with CO2− moieties. The third anomaly is a discrete change of the slopes of the wavenumber versus pressure plots for most modes observed. Further, decompression to ambient pressure generates the original Raman spectrum, showing that the pressure-induced anomalies undergone by L-leucine crystals are reversible. Copyright © 2008 John Wiley & Sons, Ltd.