Acta Crystallographica Section C

Crystal Structure Communications

Volume 69, Part 4 (April 2013)


inorganic compounds



Acta Cryst. (2013). C69, 319-323    [ doi:10.1107/S0108270113006203 ]

K and Ba distribution in the structures of the clathrate compounds KxBa16-x(Ga,Sn)136 (x = 0.8, 4.4, and 12.9) and KxBa8-x(Ga,Sn)46 (x = 0.3)

M. C. Schäfer and S. Bobev

Abstract: Studies of the K-Ba-Ga-Sn system produced the clathrate compounds K0.8(2)Ba15.2(2)Ga31.0(5)Sn105.0(5) [a = 17.0178 (4) Å], K4.3(3)Ba11.7(3)Ga27.4(4)Sn108.6(4) [a = 17.0709 (6) Å] and K12.9(2)Ba3.1(2)Ga19.5(4)Sn116.5(4) [a = 17.1946 (8) Å], with the type-II structure (cubic, space group Fd\overline{3}m), and K7.7(1)Ba0.3(1)Ga8.3(4)Sn37.7(4) [a = 11.9447 (4) Å], with the type-I structure (cubic, space group Pm\overline{3}n). For the type-II structures, only the smaller (Ga,Sn)24 pentagonal dodecahedral cages are filled, while the (Ga,Sn)28 hexakaidecahedral cages remain empty. The unit-cell volume is directly correlated with the K:Ba ratio, since an increasing amount of monovalent K occupying the cages causes a decreasing substitution of the smaller Ga in the framework. All three formulae have an electron count that is in good agreement with the Zintl-Klemm rules. For the type-I compound, all framework sites are occupied by a mixture of Ga and Sn atoms, with Ga showing a preference for Wyckoff site 6c. The (Ga,Sn)20 pentagonal dodecahedral cages are occupied by statistically disordered K and Ba atoms, while the (Ga,Sn)24 tetrakaidecahedral cages encapsulate only K atoms. Large anisotropic displacement parameters for K in the latter cages suggest an off-centering of the guest atoms.

Formula: K0.8Ba15.2Ga31.0Sn105.0, K4.3Ba11.7Ga27.4Sn108.6, K12.9Ba3.1Ga19.5Sn116.5 and K7.7Ba0.3Ga8.3Sn37.7


hkldisplay filedownload file

Structure factor file (CIF format) (25.3 kbytes)
[ doi:10.1107/S0108270113006203/bi3054K1Ba15Ga31Sn105sup2.hkl ]
Contains datablock K1Ba15Ga31Sn105


hkldisplay filedownload file

Structure factor file (CIF format) (21.4 kbytes)
[ doi:10.1107/S0108270113006203/bi3054K4Ba12Ga27Sn109sup3.hkl ]
Contains datablock K4Ba12Ga27Sn109


hkldisplay filedownload file

Structure factor file (CIF format) (21.4 kbytes)
[ doi:10.1107/S0108270113006203/bi3054K13Ba3Ga19Sn117sup4.hkl ]
Contains datablock K13Ba3Ga19Sn117


hkldisplay filedownload file

Structure factor file (CIF format) (21.7 kbytes)
[ doi:10.1107/S0108270113006203/bi3054K7Ba1Ga8Sn38sup5.hkl ]
Contains datablock K7Ba1Ga8Sn38


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