Incommensurate-Commensurate Phase Transition of Intramolecular Hydrogen-Bonded System: 5-Bromo-9-Deuteroxyphenalenone(d-BrHPLN).
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Low-temperature X-ray Weissenberg photographs of deuterated 5-bromo-9-hydroxyphenalenone (d-BrHPLN) were taken at 14.4, K to investigate the phase transition of an intramolecular and isolated hydrogen-bonded system composed of a tautomeric molecule. The system has one hydrogen bond in a rigid molecular skeleton, with the hydrogen atom being replaced by deuterium. The superlattice reflection is found at (h k+0.5 0) at 14.4, K, and it starts to deviate from the commensurate position above T<SUB>C</SUB>=22.8, K on heating. The transition is of the first kind and is characterized by a commensurate-incommensurate transition. The peak shift defined as 0.5+δ was also measured. Above T<SUB>I</SUB>=34.5, K, the profile becomes very broad and shows diffuse scattering behavior. The transition is of the second kind and is characterized by a so-called incommensurate-normal phase transition.
- Journal of the Physical Society of Japan
Journal of the Physical Society of Japan 63(12), 4286-4289, 1994
The Physical Society of Japan (JPS)