Phase transformation of ammonium monomolybdate. The structure of the low temperature modification, (NH4)2[MoO4] (mP60, P21/a)
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E. Schweda
Abstract
(NH4)2[MoO4] (mS60) undergoes on cooling a phase transition at 190 K. The investigation of this phase transition by means of time and temperature resolved X-ray powder diffraction showed that the phase transition appears on heating at a temperature of 250 K. From this hysteresis and the abrupt changes in the peak positions of the diffractograms it is assumed that this is a first order transition. A diffractogram of the low temperature modification was recorded between 10° and 100° in 2θ. The structure was determined using direct methods and was refined by Rietveld methods. The low temperature modification of (NH4)2[MoO4] (mP60, P21/a) crystallizes in space group P21/a (No. 14) and lattice constants a = 767.57(5) pm, b = 1120.53(7) pm, c = 712.64(4) pm and β = 115.727(2)°.
© 2002 Oldenbourg Wissenschaftsverlag GmbH
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Articles in the same Issue
- On the treatment of settings of space-groups and crystal structures by spezialized short Hermann-Mauguin space-group symbols
- Phase extension to weaker reflections of proteins via a partial structure based tangent formula
- Synthesis of zoning-free BaSO4-PbSO4 solid solution and its structural characterizations
- Stacking disorder in 2H-NbS2 and its intercalation compounds Kx(H2O)yNbS2 II. Stacking disorder in Kx(H2O)yNbS2
- The crystal structure of Na2Ca2Si2O7 - a mixed anion silicate with defect perovskite characteristics
- Phase transformation of ammonium monomolybdate. The structure of the low temperature modification, (NH4)2[MoO4] (mP60, P21/a)
- Topological analysis of DL-arginine monohydrate at 100 K
- Synthesis, structural and spectral studies of bis-[N-(2,4-dimethoxy benzylidene)-2-mercaptoanilinato] Ni(II)
