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

Authors: Ballirano, Paolo; Belardi, Girolamo; Maras, Adriana

Source: Neues Jahrbuch für Mineralogie - Abhandlungen, Volume 182, Number 1, November 2005 , pp. 15-21(7)

Publisher: E. Schweizerbart'sche Verlagsbuchhandlung

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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%, R_F = 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: SYNGENITE; K2CA(SO4)MIDDOTH2O; SULPHATE; FT-IR SPECTROSCOPY; X-RAY POWDER DIFFRACTION; RIETVELD METHOD

Document Type: Research article

DOI: http://dx.doi.org/10.1127/0077-7757/2005/0027

Publication date: 2005-11-01

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