ζ . Kristallogr. NCS 213 (1998) 6 6 7 - 6 6 8
667
© by R. Oldenbourg Verlag, München
C r y s t a l s t r u c t u r e o f t h e c l a t h r a t e s K s G a g S i s g a n d K s G a g S n a s
R. Kröner, К. Peters, H. G. von Schnering
Max-Planck-Institut für Festkörperforschung, Heisenbergstraße I, D-70569 Stuttgart, Germany
and R. Nesper
ΕΤΗ Zürich, Laboratorium für Anorganische Chemie, Universitätsstr. 6, CH-8092 Zürich, Switzerland Received March 3, 1998, transferred to Ist update of database ICSD in 1999, CSD-No. 409247 and 409248
Table 2. Final atomic coordinates and displacement parameters (in A^)
LK8Ga8SÎ38
Source of material: Stoichiometric mixtures of the elements were sealed in Nb/Ta capsules under Ar, heated up to 1270 К (3 h), annealed at 970 К (2-3 d) and cooled down. The grey brittle compound is a semiconductor, stable in air and against dilute acids and bases (see ref. 1). Reactions with different Ga:Si ratios gave no indications for a homogeneity range (powder patton) in contrast to ref. 2.
The refmement of the site occupancies results in the composition K8Ga/,SÌ46-n with η = 7.90 ± 0.28. Bond lenghts in the E46 net (figure): dl = 2.367(1) Kdl = 2.404(1) Â, d3 = 2.464(1) Â, d 4 = 2.447(1) Â.
GasKsSias, cubic, Ρηβη (No. 223), a =10.427(1) Λ, V=1133.6 Â ^ Z=\,R(F) =0.020, R^F) =0.017.
Table 1. Parameters used for the X-ray data collection
Crystal: grey, metallic luster, siz« 0.1 χ 0.1 χ 0.1 mm Wavelength: Mo Ka radiation (0.71069 Â)
μ: 62.0 cm-'
Diffractometer: SYNTEXPI
Scan mode: ω
293 К
20iiiax: 55°
N(AW)»iii«r: 256
Criterion for Fo. F „ > 3 o ( f „ ) ii{param)r€fimd-· 19
Program: SHF,I ,X-76
Atom Site Occ. X У ζ Un Un Uìì t/12 Un Í/23
K1 2a 0 0 0 0.0160(5) ί/ιι Un 0 0 0
K2 6d 1/4 1/2 0 0.0223(7) 0.0344(6) U22 0 0 0
El(Ga) 6c 0.566(2) 1/4 0 1/2 0.0142(4) 0.0123(3) U22 0 0 0
El(Si) 6c 0.434 1/4 0 1/2 0.0142 0.0123 U22 0 0 0
E2(Ga) I61 0.019 0.1845 X χ 0.0126 Un Un -0.0003 Í/I2 1/12
E2(Si) I61 0.981(6) 0.1845(1) X χ 0.0126(3) Un Un -0.0003(2) Un Un
E3(Ga) 24t 0.175 0 0.3058 0.1182 0.0133 0.0138 0.0134 0 0 0.0001
E3(Si) 24k 0.825(7) 0 0.3058(1) 0.1182(1) 0.0133(3) 0.0138(3) 0.0134(3) 0 0 0.0001(2)
668
Clathrates KgGaeSiss and KgGagSnsg2 . K 8 G a 8 S i i 3 8
Source o f material: For the synthesis, the chemical properties and the homogeneity range see above (KeGagSiss)· KgGaeSnss is also a semiconductor. The grey brittle crystals are larger and well- shaped with many faces (see ref. 1 ).
T h e r e f i n e m e n t o f the o c c u p a n c i e s g a v e the c o m p o s i t i o n K8GanSn46-n with η = 8.1 ± 1.3. Bond lenghts in the E46 net (figure): dl = 2 . 7 6 7 ( 2 ) λ, d2 = 2 . 7 9 1 ( 1 ) Â. d3 = 2 . 8 1 3 ( 2 ) Â and d4 = 2 . 7 3 3 ( 2 ) Â.
GaeK«Sn38, cubic, РтЪп (No. 223), a =11.935(1) Â, и=17(Ю.1 Â ^ Z=\,R(F) = 0 . 0 6 3 , Ry^F) = 0 . 0 5 9 .
Table 4. Final atomic ccwrdinates and displacement parameters (in A^)
Table 3. Parameters used for the X-ray data collection
Crystal: grey, metallic luster, size 0.1 χ 0.15 χ 0.2 mm Wavelength: Mo Ka radiation (0.71069 A)
μ: 161.9 cm"'
Diffractometer: SYNTEX PI
Scan mode: ω
'^measurement'· 293 К
2втах: 55°
ЩНк1)ш,,яие·· 378
Criterion for Fo. Fo>Jc(Fo)
^(param)refine<r· 19
Program: SHELX-76
Atom Site Occ. X У ζ Un t/22 U33 Un ί/в Uli
K l 2a 0 0 0 0.026(5) Un U22 0 0 0
K2 6d 1/4 1/2 0 0.030(8) 0.12(1) U22 0 0 0
El(Ga) 6c 0.54(1) 1/4 0 1/2 0.012(2) 0.015(1) U22 0 0 0
El(Sn) 6c 0.46 1/4 0 1/2 0.012 0.015 U22 0 0 0
E2(Ga) 16/ 0.17 0.1831 X χ 0.0134 t/ll U22 -0.0008 Un Un
E2(Sn) 16/ 0.83(3) 0.1831(1) X χ 0.0134(7) un U22 -0.0008(4) Un Un
E3(Ga) 2Ak 0.09 0 0.3130 0.1179 0.0150 0.0148 0.0140 0 0 0.0005
E3(Sn) 24k 0.91(3) 0 0.3130(1) 0.1179(1) 0.0150(8) 0.0148(8) 0.0140(8) 0 0 0.0005(6)
References
1. Kröner, R.: Zintl-Phasen der Alkalimetalle und des Bariums mit Clathrat- struktur. Dissertation, Universität Stuttgart, 1989.
2. Westerhaus, W.; Schuster, H.-U.: Temäre Phasen mit modifizierter K8Ge46-lCäfigstruktur. Z. Naturforsch. 32b (1977) 1365-1367.
3. Sheldiick, G. M.: SHELX-76, Programs for Crystal Structures Determi- nation. Cambridge 1976.
