Crystal Structure of Strontium Potassium Arsenate Octahydrate

Published

September 1, 1998

Author(s)

M Mathew

Abstract

The crystal structure of strontium potassium arsenate octahydrate, SrKAsO₄.8H₂O, has been determined by single crystal x-ray diffraction. The crystals are tetragonal, a = 7.144(1){Angstrom}, c = 23.613(2){Angstrom}, space group I4₁md (No. 109), Z = 4, V = 1205.1(1){Angstrom}³, d_c = 2.258 Mg. M^-3. The structure was refined by full-matrix least-squares techniques to R = 0.31, R_w = 0.052, for 317 reflections with I {greater than or equal} 3ς(I). All cations and anions in this compound are completely surrounded by water molecules. Sr and K ions are each coordinated to eight water molecules arranged in an approximately square antiprism. The [Sr(H₂O)₈] polyhedron shares one face of four water molecules with a [K(H₂O)₈] polyhedron forming O₄-Sr-O₄-K-O₄ polyhedra. The O₄-Sr-O₄-K-O₄ units are linked together through a pair of edge-sharing linkages of the outer water molecules, alternating along a-axis and b-axis. The hydrated cation polyhedra appear to define the host lattice, which accommodates the AsO₄ ion in the interstitial space. The environment of the AsO₄ ion consists of 16 water molecules; each oxygen atom is the acceptor in four hydrogen bonds from four water molecules. The pair distances associated with this environment may be used in investigations of the structure of hydrated XO₄ ions in solutions. Each water molecule is coordinated to one Sr and one K and hydrogen bonded to two O atoms of two different AsO₄ ions. There is no hydrogen bonding between water molecules.

Citation

Journal of Chemical Crystallography

Volume

28

Issue

No. 10

Pub Type

Journals

Keywords

crystal structure, hydrated ions, ionic hydration, strontium arsenate, struvite-type structure, struvites

Citation

Mathew, M. (1998), Crystal Structure of Strontium Potassium Arsenate Octahydrate, Journal of Chemical Crystallography (Accessed May 18, 2024)