New ternary rare earth–rhodium–germanides: Ce4Rh13Ge9 and Ho2RhGe2

Journal of Alloys and Compounds 287 (1999) L1–L3

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Letter

New ternary rare earth–rhodium–germanides: Ce 4 Rh 13 Ge 9 and Ho 2 RhGe 2 P.S. Salamakha*, O.L. Sologub Department of Inorganic Chemistry, L’ viv State University, Kyryla i Mefodia str. 6, 290005 L’ viv, Ukraine Received 8 December 1998

Abstract The structures of two new ternary germanides were determined by the single crystal X-ray diffraction. Ce 4 Rh 13 Ge 9 has an ˚ V5872.7(7) A ˚ 3 , Z52, orthorhombic structure of the Ho 4 Ir 13 Ge 9 type, Pmmn space group, a53.989(1), b511.250(3), c519.446(5) A, 3 21 ˚ m 5378.96 cm , R w 50.035 for 881 unique reflections. Ho 2 RhGe 2 has a monoclinic structure of r 59.710 g / cm , l(MoKa)50.7107 A, ˚ b 5117.22(3)8, V5405.8(6) A ˚ 3 , Z54, r 59.459 the Sc 2 CoSi 2 type, C2 /m space group, a510.4652(2), b54.2671(3), c510.2205(4) A, 3 21 ˚ m 5571.82 cm , R w 50.070 for 921 unique reflections.  1999 Elsevier Science S.A. All rights g / cm , l(MoKa)50.7107 A, reserved. Keywords: Crystal structure determination; Single crystal; X-ray diffraction; Rare earth rhodium germanides

1. Introduction

2. Experimental details and results

In a recent review on the ternary rare earth metal– transition metal–germanium systems [1] it was shown that several structure types are realised within the R–Rh–Ge systems:Yb 3 Rh 4 Sn 13 , BaNiSn 3 , CeGa 2 Al 2 , U 2 Co 3 Si 5 , Lu 2 Co 3 Si 5, Y 2 Rh 3 Ge, U 4 Re 7 Si 6 , Sc 5 Co 4 Si 10 , TiNiSi, La 3 Ni 2 Ga 2 , CeNiSi 2 , AlB 2 , Nd 4 Rh 4 Ge 3 and CeRh 12x Ge 21x . In this paper we report on the structures of two new ternary rhodium containing germanides.

Samples of nominal compositions Ce 15 Rh 50 Ge 35 and Ho 40 Rh 20 Ge 40 were prepared from high purity elements by arc melting under an argon atmosphere, annealed at 870 K in evacuated quartz tubes for 2 weeks and quenched in water. Needle-like single crystals were selected and measured using the automatic diffractometers and the conditions listed in Table 1. The final structural data for Ce 4 Rh 13 Ge 9 and Ho 2 RhGe 2 are given in Tables 2 and 3,

Table 1 Parameters for the single crystals X-ray data collections

Diffractometer type ˚ Radiation and wavelength (A) Crystal characteristics (cm) Temperature of measurements (K) ˚ 21 ) sin umax /l (A Number of measured reflections Number of unique reflections Number of reflections with Io .4s (Io ) Linear absorption coefficient (cm 21 ) Number of refined parameters R, R w Goodness of fit Structure solution program

Ce 4 Rh 13 Ge 9

Ho 2 RhGe 2

DARTCH-1 MoKa, l50.7107 0.0130.0130.005 293 0.8071 1264 881 879 378.96 87 0.051, 0.035 1.07 CSD

STOE-NICOLET MoKa, l50.7107 0.0130.0130.05 293 0.5385 1919 921 716 571.82 32 0.077, 0.070 1.46 SHELXTL

*Corresponding author. 0925-8388 / 99 / $ – see front matter  1999 Elsevier Science S.A. All rights reserved. PII: S0925-8388( 98 )01054-8

P.S. Salamakha, O.L. Sologub / Journal of Alloys and Compounds 287 (1999) L1 –L3

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Table 2 Structural data for Ce 4 Rh 13 Ge 9 of Ho 4 Ir 13 Ge 9 type, Pmmn space group, ˚ V5872.7(7) A ˚ 3 , Z52, r 5 a53.989(1), b511.250(3), c519.446(5) A, 3 ˚ m 5378.96 cm 21 , R w 50.035 9.710 g / cm , l (MoKa)50.7107 A, 2

Atom

Wyckoff notation

x

y

z

˚ ) Ueq. 310 (A

Ce1 Ce2 Ce3 Rh1 Rh2 Rh3 Rh4 Rh5 Rh6 Rh7 Rh8 Ge6 Ge1 Ge2 Ge3 Ge4 Ge5

4(e) 2(b) 2(a) 4(e) 4(e) 4(e) 4(e) 4(e) 2(b) 2(a) 2(a) 2(a) 4(e) 4(e) 4(e) 2(b) 2(a)

1/4 1/4 1/4 1/4 1/4 1/4 1/4 1/4 1/4 1/4 1/4 1/4 1/4 1/4 1/4 1/4 1/4

0.5593(2) 3/4 1/4 0.4506(3) 0.4355(3) 0.3760(3) 0.5567(4) 0.6285(3) 3/4 1/4 1/4 1/4 0.0591(5) 0.5651(5) 0.6239(4) 3/4 1/4

0.7090(1) 0.5212(2) 0.0201(2) 0.5469(2) 0.1637(2) 0.8546(2) 0.0408(2) 0.3572(2) 0.8433(3) 0.3569(3) 0.7280(2) 0.6019(4) 0.4197(2) 0.9150(2) 0.2292(2) 0.1029(3) 0.2294(4)

0.59(4) 0.53(7) 0.58(7) 0.45(4) 0.60(9) 0.45(9) 0.48(6) 0.51(7) 0.51(6) 0.46(6) 0.40(6) 0.62(9) 0.63(8) 0.61(9) 0.57(6) 0.46(9) 0.60(9)

Table 3 Structural data for Ho 2 RhGe 2 of Sc 2 CoSi 2 type, C2 /m space group, ˚ b 5117.22(3)8, V5 a510.4652(2), b54.2671(3), c510.2205(4) A, ˚ 3 , Z54, r 59.459 g / cm 3 , l (MoKa)50.7107 A, ˚ m 5571.82 405.8(6) A cm 21 , R w 50.070 Atom

Wyckoff position

x

y

z

˚ 2) Ueq. 310 (A

Ho1 Ho2 Rh Ge1 Ge2

4(i) 4(i) 4(i) 4(i) 4(i)

0.00722(1) 0.18776(1) 0.27391(3) 0.35623(3) 0.47910(3)

0 0 0 0 0

0.32971(1) 0.11429(1) 0.65433(3) 0.44022(3) 0.11625(3)

0.23(1) 0.23(1) 0.25(1) 0.26(1) 0.24(1)

Fig. 1. Projection of the Ce 4 Rh 13 Ge 9 structure on the YZ plane and coordination polyhedra of the atoms: Ce (a,b,c), Rh (d,e,f,g,h,i,j,k), Ge (l,m,n,o,p,q).

respectively. The projections of the Ce 4 Rh 13 Ge 9 and Ho 2 RhGe 2 unit cells and coordination polyhedra of the atoms are shown in Figs. 1 and 2. The descriptions of two originating structure types are presented before [2,3].

Acknowledgements This study was supported by the International Scientific Educational Program with Grants N QSU083173 and N QSU083190.

Fig. 2. Projection of the Ho 2 RhGe 2 structure on the XZ plane and coordination polyhedra of the atoms: Ho (a,b), Rh (c), Ge (d,e).

P.S. Salamakha, O.L. Sologub / Journal of Alloys and Compounds 287 (1999) L1 –L3

References [1] P.S. Salamakha, O.L. Sologub, O.I. Bodak, Ternary rare earth– germanium systems, in: K.A. Gschneidner, L. Eyring (Eds.), Handbook On the Physics and Chemistry of Rare Earths, 1999, in press.

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[2] O.L. Sologub, Yu.M. Prots’, P.S. Salamakha, V.K. Pecharskii, O.I. Bodak, J. Alloys Compd. 202 (1993) 13. [3] R.E. Gladyshevskii, O.L. Sologub, E. Parthe, J. Alloys Compd. 176 (1991) 329.