Acta Crystallographica Section C

Crystal Structure Communications

Volume 69, Part 7 (July 2013)

inorganic compounds

Acta Cryst. (2013). C69, 683-688    [ doi:10.1107/S0108270113014492 ]

Tm2.22Co6Sn20 and TmLi2Co6Sn20 stannides as disordered derivatives of the Cr23C6 structure type

A. Stetskiv, B. Rozdzynska-Kielbik and V. Pavlyuk

Abstract: A new ternary dithulium hexa­cobalt icosa­stannide, Tm2.22Co6Sn20, and a new quaternary thulium dilithium hexa­cobalt icosa­stannide, TmLi2Co6Sn20, crystallize as disordered variants of the binary cubic Cr23C6 structure type (cF116). 48 Sn atoms occupy sites of m.m2 symmetry, 32 Sn atoms sites of .3m symmetry, 24 Co atoms sites of 4m.m symmetry, eight Li (or Tm in the case of the ternary phase) atoms sites of \overline{4} 3m symmetry and four Tm atoms sites of m \overline{3} m symmetry. The environment of one Tm atom is an 18-vertex polyhedron and that of the second Tm (or Li) atom is a 16-vertex polyhedron. Tetra­gonal anti­prismatic coordination is observed for the Co atoms. Two Sn atoms are enclosed in a heavily deformed bicapped hexa­gonal prism and a monocapped hexa­gonal prism, respectively, and the environment of the third Sn atom is a 12-vertex polyhedron. The electronic structures of both title compounds were calculated using the tight-binding linear muffin-tin orbital method in the atomic spheres approximation (TB-LMTO-ASA). Metallic bonding is dominant in these compounds, but the presence of Sn-Sn covalent dumbbells is also observed.

Formula: Tm2.22Co6Sn20 and TmLi2Co6Sn20

hkldisplay filedownload file

Structure factor file (CIF format) (13.3 kbytes)
[ doi:10.1107/S0108270113014492/ku3095Isup2.hkl ]
Contains datablock I

hkldisplay filedownload file

Structure factor file (CIF format) (13.4 kbytes)
[ doi:10.1107/S0108270113014492/ku3095IIsup3.hkl ]
Contains datablock II


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