Syntheses and Structure of Gd3Rh1.940(7)In4

Autor: Ute Ch. Rodewald, Rainer Pöttgen, Rolf-Dieter Hoffmann, Mar’yana Lukachuk
Rok vydání: 2005
Předmět:
Zdroj: Monatshefte für Chemie - Chemical Monthly. 136:1985-1991
ISSN: 1434-4475
0026-9247
DOI: 10.1007/s00706-005-0375-y
Popis: The gadolinium–rhodium–indide Gd3Rh1.940(7)In4 was prepared by arc-melting of the elements and subsequent annealing in a corundum crucible in a sealed silica tube. Gd3Rh1.940(7)In4 adopts the hexagonal Lu3Co1.87In4 type, space group $P{\bar 6}$ , a = 781.4(5), c = 383.8(3) pm, wR2 = 0.0285, BASF = 0.375(1) (merohedric twinning via a twofold axis (xx0)), 648 F 2 values, 22 variables. The structure is derived from the well known ZrNiAl type through an ordering of rhodium and indium atoms on the Ni2 sites. The Rh/In ordering forces a reduction of the space group symmetry from $P{\bar 6}62m$ to $P{\bar 6}$ , leading to merohedric twinning for the investigated crystal. The Rh1 site has an occupancy of only 94.0(7)%. The investigated crystal had a composition Gd3Rh1.940(7)In4. The main geometrical motif are three types of centered, tricapped trigonal prisms, i.e., [Rh1In26Gd3], [Rh2Gd6In23], and [In1Gd6In23]. The shortest interatomic distances occur for Rh–In (276–296 pm) followed by In–In (297 pm). Together, the rhodium and indium atoms build up a three-dimensional [Rh1.940(7)In4] network, in which the gadolinium atoms fill slightly distorted pentagonal channels. The crystal chemistry of Gd3Rh1.940(7)In4 is discussed on the basis of a group-subgroup scheme.
Databáze: OpenAIRE
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