Fig. 4.

Low angle regions of the powder diffraction patterns of meta-alunogen samples obtained from alunogen by a storing over phosphorus pentoxide at 0 % RH (Debye–Scherrer transmission geometry, Cu–Kα₁) and b in situ dehydration at 60 °C (Bragg–Brentano reflection geometry, Cu–Kα_1/2). Vertical tick marks indicate the allowed peak positions for the triclinic unit cell of meta-alunogen derived from ab-initio indexing. For sake of clarity only the lines for Cu–Kα₁ radiation are plotted. Differences in relative intensities are due to preferred orientation (see text)