title: Examination of l-Glutamic Acid Polymorphs by Solid-State Density Functional Theory and Terahertz Spectroscopy.
abstract: The ability of l-glutamic acid to crystallize in two different forms has long been the subject of study due to its commercial importance. While a solvent-mediated phase transformation between the α and β polymorphs is the prevailing theory, recent reports indicate a thermal solid-solid transformation between the two may be possible. However, determining accurate thermodynamic stabilities of these crystals has been challenging. Here new low-temperature single-crystal X-ray diffraction data coupled to solid-state density functional theory simulations have enabled a detailed description to be achieved for the energetic parameters governing the stabilization of the two l-glutamic acid solids. The temperature-dependent Gibbs free-energy curves show that α-glutamic acid is the preferred form at low temperatures (<222 K) and the β form is most stable at ambient temperatures. Terahertz time-domain spectroscopy was utilized to evaluate the quality of the intermolecular force modeling as well as to provide characteristic low-frequency spectral data that can be used for quantification of polymorph mixtures or crystal growth monitoring.
authors: Department of Chemistry, Syracuse University , 1-014 Center for Science and Technology, Syracuse, New York 13244-4100, United States.
authors: Michael T
authors: MT
authors: Ruggiero
authors: Department of Chemical Engineering and Biotechnology, University of Cambridge , New Museums Site, Pembroke Street, Cambridge CB2 3RA, United Kingdom.
authors: Juraj
authors: J
authors: Sibik
authors: Department of Chemical Engineering and Biotechnology, University of Cambridge , New Museums Site, Pembroke Street, Cambridge CB2 3RA, United Kingdom.
authors: J Axel
authors: JA
authors: Zeitler
authors: Department of Chemistry, Syracuse University , 1-014 Center for Science and Technology, Syracuse, New York 13244-4100, United States.
authors: Timothy M
authors: TM
authors: Korter
mesh_terms: D003198:Computer Simulation; D003460:Crystallization; D018698:Glutamic Acid / Q000737:chemistry*; D006860:Hydrogen Bonding; D008956:Models, Chemical; D015394:Molecular Structure; D055068:Terahertz Spectroscopy; D013816:Thermodynamics; D014961:X-Ray Diffraction
chemical_list: D018698:Glutamic Acid