Scientific article

Local atomic order in the vicinity of Cu2 dumbbells in TbCu7-type YCu6.576 studied by Bragg and total scattering techniques

Published inIntermetallics, vol. 17, no. 10, p. 818-825
Publication date2009

The crystal structure of YCu6.576, a hyperstoichiometric substitution variant of the CaCu5-structure type, was shown to contain Cu2 dumbbells replacing Y-atoms in a fraction s = 0.19 in the formula Y1−sCu5+2s. The structure type TbCu7 is assigned to the disordered structure (P6/mmm, a = 4.96 Å, c = 4.15 Å). The local order in the vicinity of the Cu2-dumbbells has been derived from total scattering X-ray synchrotron data via refinement of the atomic pair distribution function (PDF). The coordinating Cu6-hexagon around the dumbbell site shows a shrinkage of 0.33(1) Å w.r.t. the equivalent environment of the Y-atom. No adjacent Y-atoms are substituted but a hexagonal arrangement of Cu2-dumbbells, separated at least by the vectors √3a and √3b exists in layers perpendicular to c. The stacking along [001] is random and can be modeled locally from the PDF data consistent with both ab- and abc-type stacking. Therefore, the local order is comparable to that in Ni17Th2- and Th2Zn17-structure types. X-ray single crystal analysis and Rietveld refinements of neutron- and X-ray powder data (Bragg diffraction data) of YCu6.576 are consistent with the findings from local crystallography (total scattering data) answering a long-standing question in disordered CaCu5-type based intermetallic structure variants.

  • Intermetallics
  • Miscellaneous
  • Crystallography
  • Diffraction
  • Order/disorder transformations
  • Site occupancy
Research group
Citation (ISO format)
CERNY, Radovan, FILINCHUK, Yaroslav, BRÜHNE, Stefan. Local atomic order in the vicinity of Cu<sub>2</sub> dumbbells in TbCu<sub>7</sub>-type YCu<sub>6.576</sub> studied by Bragg and total scattering techniques. In: Intermetallics, 2009, vol. 17, n° 10, p. 818–825. doi: 10.1016/j.intermet.2009.03.010
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Article (Published version)
ISSN of the journal0966-9795

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