REFINEMENT OF THE CRYSTAL-STRUCTURE OF SYNTHETIC MARIALITE

The crystal structure of synthetic marialite prepared by a solid-phase synthesis at high pressures is refined by the Rietveld method using t he X-ray powder diffraction data (ADP-2 diffractometer; lambda CuKalph a; Ni filter; 12.00 degrees < 2 theta < 135.00 degrees; 28 step, 0.02 degrees; count time per step, 5 s; 1059 Bragg reflections). All calcul ations are performed with the WYRIET program (version 3.3) in space gr oup 14/m. The unit-cell parameters [a = 12.0391(1) and c = 7.5421(1) A ngstrom, V= 1093.16(2) Angstrom(3)] correspond to the parameters of th e end member in the marialite-meionite series of solid solutions and c an serve as references. The structure of synthetic marialite is refine d in the anisotropic approximation (the Pearson function) to R-p = 4.7 5, R-wp = 6.34, R-B = 2.04, R-F = 3.03, s = 1.13, DWD = 1.68, and sigm a(x)= 1.484. The diffraction data (40 reflections) are presented.