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].
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
