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DOE OSTI2020

Materials Data on K2S2O5 by Materials Project

K2S2O5 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to seven O2- atoms to form distorted edge-sharing KO7 pentagonal bipyramids. There are a spread of K–O bond distances ranging from 2.74–3.00 Å. In the second K1+ site, K1+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of K–O bond distances ranging from 2.86–3.27 Å. There are two inequivalent S4+ sites. In the first S4+ site, S4+ is bonded in a water-like geometry to two equivalent O2- atoms. Both S–O bond lengths are 1.51 Å. In the second S4+ site, S4+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. All S–O bond lengths are 1.49 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to four K1+ and one S4+ atom. In the second O2- site, O2- is bonded in a 1-coordinate geometry to three K1+ and one S4+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to three K1+ and one S4+ atom.

36 MATERIALS SCIENCE↗

NASA NTRS1983

Thermodynamics of the potassium-sulfur-oxygen and related systems

The chemical reactions which occur when potassium sulfide, K2S, and potassium sulfite, K2SO3, are heated at temperatures where their vapor pressures are significant, were studied and the vapor pressures and the partial pressures of the chemical products were measured. Mass spectrometry of the vapor of potassium sulfide revealed only K(g). X-ray studies of the solid residues from vaporization experiments revealed K2S2(s) and chemical analyses of the same solid residues showed that the residues approached a composition K2Sx with x in the range 3-4. Vapor pressure of K2S was measured by simultaneous Knudsen-effusion and torsion-effusion (SKETE) in crucibles of aluminum oxide and of graphite. In each such experiment, the vapor pressures agreed initially, but then the apparent pressure by Knudsen-effusion increased suddenly and remained much greater than that by torsion-effusion for the remainder of the experiment. Results of third-law analysis of the torsion pressures imply a delta H (298K) of formation of K2S(s) of -364 + or - 12 kJ/mol. Vapor pressures over K2SO3(s) were measured by simultaneous Knudsen and torsion-effusion and by mass spectrometry. The vapor pressures of both K2S2O5(s) and K2SO3(s) were nonreproducible at a given temperature due to the vaporization reactions of the materials being irreversible under conditions in effusion cells.

Edwards, J. G.↗