PREPARATION AND CRYSTAL STRUCTURE OF THE TERNARY CARBIDES R12Os5C15 with R = Y, Pr, Nd, Sm, Gd-Tm and Ln4-xOs1+yC6 with Ln = La-Nd, Sm)
Thomas Hüfken, K.H. Wachtmann and W. Jeitschko
Anorganisch-Chemisches Institut, Universität Münster, Wilhelm-Klemm-Straße 8, D-48149 Münster, Germany
Many ternary rare earth (R) transition
metal (T) carbides have been reported in recent years,
e.g. the series R3.67TC6 with T = Mn, Fe, Ru [1], R2ReC2 [2], R12Mn5C15 [3], R5Re2C7
[4] and references in these publications. With osmium as
transition metal component only two series have been communicated
up to now: the series R5Os3C4-x with a new kind of filled Mn5Si3 type structure [5] and R2OsC2 [6], which is isotypic with Pr2ReC2 [7]. Now we report on two new series of ternary rare
earth osmium carbides: R12Os5C15, which is isotypic with La12Re5C15 [8], and
R4-xOs1+yC6 with a structure similar to that of La3.67FeC6 [1].
The ten carbides R12Os5C15 (R = Y, Pr, Nd, Sm, Gd-Tm) (Fig. 1) have been prepared by arc-melting cold-pressed pellets of the elemental components with subsequent annealing. Their structure was refined from powder diffractometer data of Tb12Os5C15: P6_2m, a = 1069.4(1) pm, c = 507.95(6) pm, Z = 1, RF = 0.033 for 134 reflections and 12 atomic parameters (Fig. 2.).
The compounds Ln4-xOs1+yC6
(Ln = La-Nd, Sm) were also prepared by arc-melting cold-pressed
pellets of the elemental components and subsequent annealing.
They are isotypic with La3.67FeC6 [1]. Fig. 3 shows the plot of the cell volumes together
with the cell volumes of the isotypic manganese, iron and
ruthenium compounds.
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| Fig. 1. Cell volumes of La12Re5C15 type carbides. | Fig. 2. The La12Re5C15 type structure of Tb12Os5C15. Single-digit numbers correspond to the atom designations. The trigonal-planar polyanionic groups (Os1)3(C4)3(C2=C3)3 and Os2(C1)3 are emphasized in the lower part of the figure. |
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| Fig. 3. Cell volumes of La3.67FeC6 type carbides. |
