Proton disorder in NH···N bonded [dabcoH]+I− relaxor: new insights into h-disordering in a one-dimensional H(2)O ice analogue

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dc.contributor.authorKatrusiak, Aen_AU
dc.contributor.authorSzafranski, Men_AU
dc.contributor.authorMcIntyre, GJen_AU
dc.date.accessioned2012-04-17T02:09:27Zen_AU
dc.date.available2012-04-17T02:09:27Zen_AU
dc.date.issued2010-10-01en_AU
dc.date.statistics2012-04-17en_AU
dc.description.abstractProtons in the NH+···N hydrogen bonds linking the cations into strictly linear aggregates in the crystal of 1,4-diazabicyclo[2.2.2]octane hydroiodide ([C6H13N2]+·I−, dabcoHI) remain disordered, and the average crystal symmetry (space group P6̅m2) remains unchanged, down to 1.5 K, as evidenced by single-crystal neutron-diffraction, but against the expectation based on the third law of thermodynamics. This proton disorder reveals the role of the thermal-activation and proton-tunneling processes for the polarizability of hydrogen bonds and for the formation of polar nanodomains, resulting in the unique property of an anisotropic giant dielectric response in the chemically homogeneous compound. The dielectric constant exceeding several thousand in the direction of the crystal [z] axis between 150 and 300 K can be explained by the fluctuations of nanodomains, whereas the dielectric constant of about 100 at 10 K can be due to the residual contribution of tunneling protons in hydrogen bonds. The proton transfers disproportionate the dabco monocations into dications and neutral molecules and generate high crystal-field fluctuations. The consideration of possible crystal-symmetry changes shows that ferroelectric proton ordering would lead to the lowered symmetry of space group P3m1 within the hexagonal system, and antiferroelectric proton ordering would require a transformation to an orthorhombic phase; however, the proton-site correlations are too weak for these transformations to take place, and the resultant structure remains disordered. The crystal symmetry and the lack of Fowler−Bernal rules distinguish dabcoHI from the H2O ice-Ih, and are essential for the dielectric properties of this substance © 2010, American Chemical Societyen_AU
dc.identifier.citationSzafranski, M., Katrusiak, A., McIntyre, G. J., (2010). Proton disorder in NH···N bonded [dabcoH]+I− relaxor: new insights into h-disordering in a one-dimensional H(2)O ice analogue. Crystal Growth & Design, 10(10), 4334-4338. doi:10.1021/cg100247gen_AU
dc.identifier.govdoc4282en_AU
dc.identifier.issn1528-7483en_AU
dc.identifier.issue10en_AU
dc.identifier.journaltitleCrystal Growth & Designen_AU
dc.identifier.pagination4334-4338en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/4134en_AU
dc.identifier.urihttps://doi.org/10.1021/cg100247gen_AU
dc.identifier.volume10en_AU
dc.language.isoenen_AU
dc.publisherAmerican Chemical Societyen_AU
dc.subjectHydrogenen_AU
dc.subjectCrystalsen_AU
dc.subjectAnisotropyen_AU
dc.subjectHexagonal latticesen_AU
dc.subjectPermittivityen_AU
dc.subjectMonocrystalsen_AU
dc.titleProton disorder in NH···N bonded [dabcoH]+I− relaxor: new insights into h-disordering in a one-dimensional H(2)O ice analogueen_AU
dc.typeJournal Articleen_AU
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