Local atomic order in the vicinity of Cu2 dumbbells in TbCu7-type YCu6.576 studied by Bragg and total scattering techniques
(2009) Intermetallics — Vol. 17, n° 10, p. 818-825 (2009)
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- Abstract
- 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.
- Affiliations
ESRF, Grenoble (France) Chimie
Citations
Cerny, R., Filinchuk, Y., & Brühne, S. (2009). Local atomic order in the vicinity of Cu2 dumbbells in TbCu7-type YCu6.576 studied by Bragg and total scattering techniques. Intermetallics, 17(10), 818-825. https://doi.org/10.1016/j.intermet.2009.03.010 (Original work published 2009)