Sodium hydrogencarbonate (NaHCO3): coincidence-site lattice twinning and structure refinement
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Michael E. Fleet
Abstract
Sodium hydrogencarbonate (NaHCO3) has been recrystallised hydrothermally using a cooling ramp from 250 °C to 190 °C at 0.069 GPa, and investigated by single crystal X-ray diffraction at room temperature and pressure. Representative crystal data are: monoclinic, space group P21/n, Z = 4, a = 7.4688(4), b = 9.6842(6), c = 3.4791(2) Å, β = 93.321(2)°, R = 0.026, and Dx = 2.221 g/cm3. The crystals investigated are complexly twinned by reticular pseudomerohedry, but give two coincidence-site lattices with pseudocell parameters: a = 3.4791(2), b = 9.6842(6), c = 29.875(2) Å, β = 93.321(2)°, twin axis [001], twin index (Σ) = 4; and, a = 8.4360(6), b = 9.6811(7), c = 24.941(2) Å, β = 99.109(5)°, twin axis [10-1], Σ = 8. The Σ = 4 and Σ = 8 twins occur in separate twinned crystals but in similar twin proportions (5.5 : 1), and are most likely secondary in origin. The two coincidence-site lattices are permitted in NaHCO3 because β corresponds closely to the theoretical value given by the positive root of [sin2 (β – π/2) = 3/912].
© by Oldenbourg Wissenschaftsverlag, München, Germany
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Articles in the same Issue
- Point groups in crystallography
- Non-hydrostatic compression of zeolite NaA in water medium: connection to anomalous conductivity
- Sodium hydrogencarbonate (NaHCO3): coincidence-site lattice twinning and structure refinement
- Crystal chemistry and topology of Rb–MIII molybdates (M = Fe, Sc, In) and triclinic Rb2Mo4O13: novel building blocks, decorated chains and layers
- Structural, spectroscopic and EPR studies of tetraethylammonium tetramethylammonium tetrabomocuprate (II) complex
- Synthesis and structure of [Nd(C6NO2H5)3(H2O)2]2n· (3nHgCl4) · (4nH2O)
- 1,4-diazabicyclo[2.2.2]octane-1,4-diium dihydrogen phosphate monohydrate from X-ray and neutron data
- On the concept of long range order in solids: The use of algorithmic complexity
