Pressure-induced phase transitions in l-alanine, revisited

N. A. Tumanov, E. V. Boldyreva, B. A. Kolesov, A. V. Kurnosov, R. Quesada Cabrera

Research output: Contribution to journalArticle

Abstract

The effect of pressure on l-alanine has been studied by X-ray powder diffraction (up to 12.3 GPa), single-crystal X-ray diffraction, Raman spectroscopy and optical microscopy (up to ∼6 GPa). No structural phase transitions have been observed. At ∼2 GPa the cell parameters a and b become accidentally equal to each other, but without a change in space-group symmetry. Neither of two transitions reported by others (to a tetragonal phase at ∼2 GPa and to a monoclinic phase at ∼9 GPa) was observed. The changes in cell parameters were continuous up to the highest measured pressures and the cells remained orthorhombic. Some important changes in the intermolecular interactions occur, which also manifest themselves in the Raman spectra. Two new orthorhombic phases could be crystallized from a MeOH/EtOH/H2O pressure-transmitting mixture in the pressure range 0.8-4.7 GPa, but only if the sample was kept at these pressures for at least 1-2 d. The new phases converted back to l-alanine on decompression. Judging from the Raman spectra and cell parameters, the new phases are most probably not l-alanine but its solvates.

Original languageEnglish
Pages (from-to)458-471
Number of pages14
JournalActa Crystallographica. Section B: Structural Science
Volume66
Issue number4
DOIs
Publication statusPublished - 2010
Externally publishedYes

Keywords

  • Amino acids
  • Phase transitions
  • Polymorphism
  • Pressure

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