Pressure-induced phase transitions in L-alanine and DL-alanine, revisited
(2011) XXII International Congress and General Assembly of the IUCr — Location: Madrid, Spain (22.August.2011)
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- The effect of pressure on L-alanine and DL-alanine has been studied by X-ray powder diffraction, single-crystal X-ray diffraction, Raman spectroscopy and optical microscopy. No previously reported structural phase transitions in L-alanine and DL-alanine have been observed up to 12.3 and 8.3 GPa, respectively. In both compounds at about 1.5-2 GPa (close to the pressure of the previously reported phase transition in L-alanine into a tetragonal phase, 2.3 GPa [1], [2]), the cell parameters a and b become accidentally equal to each other, but without a change in the space group symmetry. Neither could be a polymorphic transformation in L-alanine from tetragonal into a monoclinic phase at about 9 GPa confirmed, the changes in the cell parameters till the highest measured pressures being continuous and the cell metrics remaining orthorhombic. Our Raman experiments confirmed the effects described previously for the spectra of L-alanine [1] and DL-alanine [3], but we have shown that the spectral changes are continuous and are not related to structural phase transitions. During a slow decompression of L-alanine single crystal (in a methanol-ethanol 4:1 mixture as a pressure-transmitting liquid) from about 6 GPa, new phases crystallized in the diamond anvil cell in the pressure range between 0.8-4.7 GPa, which recrystallized into L-alanine below 0.8 GPa. These previously unknown phases were characterized by powder X-ray diffraction and Raman spectroscopy and seem to be a solvate of L-alanine. The study was supported by a grant from RFBR (09-03-00451), a BRHE grant RUX0-008-NO-06, a FASI Contract № 02.740.11.5102 and Integration Projects SB RAS (№13 & 109). [1] A.M.R. Teixeira, P.T.C. Freire, A.J.D. Moreno, J.M. Sasaki, A.P. Ayala, J. Mendes Filho, F.E.A. Melo, Solid State Commun., 2000, 116, 405-409. [2] J.S. Olsen, L. Gerward, P.T.C. Freire, J. Mendes Filho, F.E.A. Melo, A.G. Souza Filho, J. Phys. Chem. Solids, 2008, 69, 1641-1645. [3] E.A. Belo, J.A. Lima Jr., P.T.C. Freire, F.E.A. Melo, J. Mendes Filho, H.N. Bordallo, A. Polian, Vibr. Spectr., 2010, 54, 107-111.
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Tumanov, N., Boldyreva, E., Kurnosov, A., & Quesada Cabrera, R. (2011). Pressure-induced phase transitions in L-alanine and DL-alanine, revisited. Acta Crystallographica. Section A, Foundations of Crystallography, A67(1), C503. https://hdl.handle.net/2078.5/191572 (Original work published 2011)