The crystal structure and one-dimensional disorder of the orange modification of HgI2
Abstract
The metastable orange modification of HgI2, described earlier by several authors, was obtained by recrystallization of HgI2 from 2-chloroethanol in the form of square, platelike crystals ranging in color from red-orange to yellow-orange. The x-ray photographs of the yellow-orange crystals indicated one-dimensional disorder along c, whereas the reflections from the red-orange form were sharp. The Friedel symmetry is 4/mmm and the lattice constants are twice those of the red form, i.e., a = 8.776, c = 24.723 Å, c/a≃;2√2. Both the hk0 and hhl reciprocal-net planes are identical with the hk0 plane of the red form and there are many systematic extinctions. The structure was solved from these observations. The structural motif is a Hg4I10 group, consisting of four corner-linked HgI4 tetrahedra in a tetrahedral arrangement. These groups are connected into HgI2 layers which are stacked with I–I contacts in the same way as the HgI4 tetrahedra in the red form. In contrast to the red form, there exist two kinds of stacking, leading to a cubic close packing of the iodine atoms. One results in a four-layer structure (red-orange crystals), the other in a two-layer structure. The disorder of the yellow-orange crystals is caused by an irregular succession of the two kinds of stacking. The intensity of the diffuse scattering arising from the disorder was calculated, and is in qualitative agreement with the observations.
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Articles in the same Issue
- Omission solid solution in magnetite: Kenotetrahedral magnetite*
- Die Kristall- und Molekülstruktur von Phyllochlorinester
- Über den Einfluß der Übersättigung auf das Wachstum von KCl-Einkristallen in reinen wässerigen Lösungen*
- Stoichiometry, cation coordination number and a method of representation of oxide compounds and phases related to the fluorite structure
- Die Kristallstruktur von Li4GeO4
- Über ilmenitähnliche Phasen im System MgO–Sb2O5 und die Lichtabsorption von Ni2+ und Co2+ im Gitter von Mg7Sb2O12
- Der Monochromatisierungsfehler balancierter Filter bei photographischer Registrierung
- The crystal structure and one-dimensional disorder of the orange modification of HgI2
- Die Kristallstruktur des 2.6-Diphenyl-4-(4-bromphenyl)-N-(p-oxy-m,m′-diphenyl)-phenyl-pyridinium-betain-monoäthanolats
- Accurate Bragg intensities for uracil: a thermal parameter refinement
- Intensitätsauswertung von Einkristall-Röntgenaufnahmen Erweiterung eines Verfahrens von Kaan und Cole
- Phasenumwandlung von AlB10
- Angle calculation for a four-circle diffractometer
