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Reply to comment on Couzi et al . (2018): a phenomenological model for structural phase transitions in incommensurate alkane/urea inclusion compounds

DOI: 10.1098/rsos.190518 DOI Help

Authors: Kirsten Christensen (University of Oxford) , P. Andrew Williams (Cardiff University) , Rhian Patterson (Cardiff University; Diamond Light Source) , Benjamin A. Palmer (Weizmann Institute of Science) , Michel Couzi (CNRS, Université de Bordeaux) , Francois Guillaume (CNRS, Université de Bordeaux) , Kenneth D. M. Harris (Cardiff University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Royal Society Open Science , VOL 6

State: Published (Approved)
Published: August 2019
Diamond Proposal Number(s): 21340

Open Access Open Access

Abstract: In a recent paper (Couzi et al. 2018 R. Soc. open sci.5, 180058. (doi:10.1098/rsos.180058)), we proposed a new phenomenological model to account for the I↔II↔“III” phase sequence in incommensurate n-alkane/urea inclusion compounds, which represents an alternative interpretation to that proposed in work of Toudic et al. In a Comment (Toudic et al. 2019 R. Soc. open sci.6, 182073. (doi:10.1098/rsos.182073)), Toudic et al. have questioned our assignment of the superspace group of phase II of n-nonadecane/urea, which they have previously assigned, based on a (3 + 2)-dimensional superspace, as C2221(00γ)(10δ). In this Reply, we present new results from a comprehensive synchrotron single-crystal X-ray diffraction study of n-nonadecane/urea, involving measurements as a detailed function of temperature across the I↔II↔“III” phase transition sequence. Our results demonstrate conclusively that “main reflections” (h, k, l, 0) with h+k odd are observed in phase II of n-nonadecane/urea (including temperatures in phase II that are just below the transition from phase I to phase II), in full support of our assignment of the (3+1)-dimensional superspace group P212121(00γ) to phase II. As our phenomenological model is based on phase II and phase “III” of this incommensurate material having the same (3+1)-dimensional superspace group P212121(00γ), it follows that the new X-ray diffraction results are in full support of our phenomenological model.

Journal Keywords: superspace groups; incommensurate composite materials; urea inclusion compounds; solid-state phase transitions

Subject Areas: Chemistry


Instruments: I19-Small Molecule Single Crystal Diffraction

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