Abstract
The phase transition of E-vanillyl oxime {1-[(E)-(hydroxyimino)methyl]-4-hydroxy-3-methoxybenzene, C8H9NO3} has been analysed by single-crystal and powder X-ray diffraction. The high-temperature (HT) phase (P21/a, Z′ = 1) transforms into the low-temperature (LT) phase (threefold superstructure, P\overline{1}, Z′ = 6) at ca 190 K. The point operations lost on cooling, {m
[010], 2[010]}, are retained as twin operations and constitute the twin law. The screw rotations and glide reflections are retained in the LT phase as partial operations acting on a subset of Euclidean space {\bb E}^3. The full symmetry of the LT phase, including partial operations, is described by a disconnected space groupoid which is built of three connected components.
Publisher
International Union of Crystallography (IUCr)
Subject
Materials Chemistry,Metals and Alloys,Atomic and Molecular Physics, and Optics,Electronic, Optical and Magnetic Materials
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