Refinement of crystal structures of scapolites by the Rietveld method: marialites (6.4, 8.1, and 15.0% Me1)

The structures of three Pamir Na- and Cl-enriches scapolites with the meionite component reaching up to 6.4, 8.1, and 15.0% Me, respectively, are refined by the Rietveld method (ADP-2 diffractometer, λCuKα radiation, Ni-filter, 9.00 deg. <2θ<150.00 deg. , scanning step 0.02 deg. 2θ, exposure at a point 5 s, number of reflections (α1+α2) 952-1225). The calculations were performed by the WYRIET program. Version 3.3 within the sp. gr. I4/m. The unit-cell parameters obtained are a=12.0489(3), 12.0546(2), 12.0413(1); and c=7.5665(2), 7.5684(2), and 7.5809(2) A, respectively. The marialite structures are refined in the anisotropic approximation with Rp=4.73-5.32, Rwp=6.17-7.28, RB=2.31-2.86, RF=2.43-3.22, s=1.31-2.09, DWD=0.68-1.36, and σx=1.720-2.329. The difference electron-density maps showed additional maxima indicating the presence of additional volatile components in the structure channels