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# Ice XI: The ordered form of ICE Ih

Howe, Rachel (1988)
Ph.D. thesis, University of Birmingham.

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## Abstract

The history of the development of the understanding of the statistical arrangement of hydrogen bonds in ice Ih and the discovery of the transition at 72 K to the ordered phase, ice XI, catalysed by alkali hydroxide doping, is reviewed. Possible ordered arrangements of hydrogen bonds are discussed and enumerated. A theory is presented relating the entropy and permittivity of partially ordered ice to the degree of order. The apparatus developed for dielectric experiments on KOH-doped ice is described. The results of such measurements for polycrystalline specimens and one single crystal are presented. Measurements above the transition reveal that the main charge carriers are OH$$^-$$ ions, with a temperature-independent mobility of approximately 10$$^-$$$$^1$$$$^0$$ m$$^2$$ v$$^-$$$$^1$$ s$$^-$$$$^1$$. The transformation to the ordered phase starts when the sample is cooled below about 65 K, and once started can be speeded up by heating the sample to 67-70 K: the static permittivity and the a.c. conductivity slowly decrease. Neutron powder diffraction experiments were performed on HRDP at ISIS. After one unsuccessful experiment, dielectric measurements on powder samples showed the importance of excluding CO$$_2$$ during preparation. In a second experiment the structure of ice XI was confirmed and the lattice parameters determined for the first time.

Type of Work: Ph.D. thesis. Whitworth, R.W Faculties (to 1997) > Faculty of Science School of Physics and Space Research Ice, Ice XI, neutron diffraction, phase transition, dielectric properties, partial order QC PhysicsQD Chemistry University of Birmingham 5255
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