On the first incommensurate ordering of NH4Cu7-xS4

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The first incommensurate ordering of NH4Cu7-xS4 (x = 0.16) has been investigated using X-ray single crystal diffraction at 174 K. The modulated structure is described with monoclinic symmetry with the cell parameters a = 10.272 (angstrom), b = 10.272 (angstrom), c = 7.694 (angstrom) and β=90.0°. It belongs to the four-dimensional space group P:P2/n:-11 {conventional setting P:P2/b:-11 (no. 13.1)}. The incommensurate modulation to the lattice (q approx. 0.39, 0, 0) appears to be caused by the sub-stoichiometry of copper. A DSC-study of the isostructural TlCu7-xS4 relates the thermal behaviour of the two thiocuprates to changes in the copper content. A tentative 'phase stability diagram' for such compounds is presented.


  • L. Norén
  • R. Berger
  • S. Lidin
  • L. Eriksson
  • J. Huster
  • V. Petříček
External organisations
  • Uppsala University
  • Stockholm University
  • RWTH Aachen University
  • Institute of Physics of the Czech Academy of Sciences
Original languageEnglish
Pages (from-to)102-109
Number of pages8
JournalJournal of Alloys and Compounds
Issue number1-2
Publication statusPublished - 1999 Jun 29
Publication categoryResearch
Externally publishedYes