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Durham University

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Publication details for Prof. Ivana Evans

Evans, Ivana Radosavljevic, Howard, Judith A. K. & Evans, John S. O. (2008). Structural ferroelectric phase transition and polymorphism in 2-aminopyridine dihydrogen phosphate. Crystal Growth and Design 8(5): 1635-1639.

Author(s) from Durham


The structural ferroelectric phase transition in 2-aminopyridine dihydrogen phosphate (2APP) has been studied by single crystal and powder X-ray diffraction between room temperature and 16 K. It has been shown that α-aminopyridine dihydrogen phosphate (α-2APP) undergoes a transition from the centrosymmetric space group C2/c in the paraelectric phase to the polar space group Cc in the ferroelectric phase. This is a second-order phase transition associated with ordering of protons in short O−H···O hydrogen bonds. This system is found to exhibit rich polymorphism: depending on crystallization conditions, three anhydrate forms and one monohydrate can be isolated. 2APP hydrate and γ-2APP have been identified for the first time, and their structures have been solved from single crystal diffraction data.