Original paper

Refinement of the structure of synthetic syngenite K2Ca(SO4)2H2O from X-ray powder diffraction data

Ballirano, Paolo; Belardi, Girolamo; Maras, Adriana

Abstract

The refinement of the crystal structure of synthetic syngenite K2Ca(SO4)·H2O has been carried out through the Rietveld method on X-ray powder diffraction data. Space group is P21/m, a = 9.7710(2) Å, b = 7.1449(2) Å, c = 602469(1) Å, β = 103.992(2). Conventional agreement indices are Rp = 5.26%, wRp = 7.02%, RF = 3.91%, reduced χ2 = 1.185. The structure consists of an alternation of sheets made of columns of KO8 polyhedra linked by zig-zag chains of CaO9 polyhedra and by two independent sulfate groups S1 and S2. Both Ca and K cations coordinates the water molecular and each H forms a hydrogen-bond with O4. The Ow…O4 distance of 2.69(1) Å is in good agreement with 2.75 Å dervied from IR measurements.

Keywords

syngenitek2ca(so4)middoth2osulphateft-ir spectroscopyx-ray powder diffractionrietveld method